Custom  Fiberglassed  Lower  Door  Panels

First off, make a trim panel for the entire bottom of the door, something like this. I fitted it exactly to match the stock one.  it's easiest to just trace the stock one onto a piece of 1/4" MDF (1/4" hardboard is what I used) and then cut it out with a jigsaw. I used 1/4" T-Nuts to fasten it to the door panel. If your not sure what T-Nuts are, go to the hardware store and just ask, they should have them.  You can see they are inserted into the wood by drilling a hole *slightly* smaller than the nut, then hammering it into the wood from the top.  The bolt goes from the back of the door panel, into the t-nut, and then it should be bolted in place. Make sure you have a good fit before you move any further.  Put it on and off many times, until you have the perfect fit, then trace one for the other door off of the first one, so they are both the same.  However, each door make require slightly different fitments, and slightly different sanding in some areas

Next, make some trim rings to fit the speakers you want to mount in there. I used 1" thick wood, and then routed out the inner edge, so that it would be a "flush mount" when I was finished.

You can also just use a circular ring, and not route out the insides for a flush mount, just a flat ring will work fine.

Notice the edges, for the flush mount finish.  This is a different backing piece, but actually the EXACT SAME trim ring used for the door panels, I made 4 exactly the same, at the same time.

Mount the trim ring to the new lower door panel using "stilts" of wood, cut to the proper height for whatever angle and placement you want the speakers to be aimed. I choose to Hot Glue the mounts in place, and then screw them in after finding the exact fitment I wanted. By hot gluing first, I could rip it off if I didn't like the way it lined up, and redo it easily.  But once I got it right, I screwed it into place to hold it tightly. Using an air powered brad-nailer works the best, sometimes screws tend to be a bit bulky and will crack the stilts, even if you have predrilled the holes. However, make sure that the ring is very secure. Once you start stretching the fabric over it, you'll need to make sure it stays in place.

After it is in place, stretch your cloth over the entire thing, and staple into place. The more staples, the better.  It is best to use some stretchy cloth, such as sweatshirt material, grill cloth, discounted Fleece from the Wal-Mart fabric dept. (that's what I did)

After the cloth is in place, and has the correct form you want, start applying FiberGlass resin to the mold.  I bought some Fiberglassing resin at FleetFarm, and mixed it according to the directions on the bottle.  I bought a whole bunch of cheapo brushes from the dollar store to apply the resin with, because once you use the brush, it's done.  After this shit hardens, it'd HARD! (if you want, you can keep the brush for a few applications by soaking it in acetone between layers of resin)

Resin both the outside and inside, if possible, to make sure it is fully saturated. The wetter the better! If you get a thick enough fleece and properly soak it, you may not even need to reinforce it.  (hint: 100% polyester fleece and polyester resin will make a super strong finished product)

Once your first layer of resin has tacked up, you can start doing the actual fiber glass reinforcing if needed.  Cut the fiberglass matte into small pieces, approx. 4"x8" (or whatever size fits the area you need to cover).  Now, there are two ways of laying the matting, experiment to see what works for you. Method One: "Brushing". Brush some resin onto your mold, and then lay the fiberglass piece over it. Brush more resin onto the piece to make sure it is FULLY saturated. Smooth it out so there are NO bubbles. Method Two: "Wetting out the matting".  Pour some resin into a small pan, about 1/4" of resin in a disposable 9x9 cooking tin works good. Drop your pieces of matting into the resin and completely saturate it. Lift if out and apply to your mold.  Smooth it out and do another.  Bubbles are VERY VERY bad, use a squeegee if you need to smooth it out.  MAKE SURE THERE ARE NO BUBBLES. Bubbles mean you have air trapped in-between the pieces, and if your pieces are not right on top of each other, there is no structure there, and that area will be a weak spot.

Completely cover the entire area you are molding with fiberglass. You may need up to 4-5 layers of fiberglass matte/resin on the entire piece to make sure it is hard enough to withstand the abuse of opening/closing the door all day.

You can let the matte go over the edges, once it hardens, you can just trim it off with a knife, razor, and grinding bit.  Make sure you have a good solid piece once you are finished. After you have all your layers done, and it is hard enough, sand down all the really high spots, and bumps, etc etc.

After you get the "rough sanding" done, start with body filler.  Put it on thick, one layer at a time, and then when it hardens, sand like crazy until it starts to take shape.  You'll probably need 4-5 layers of the body filler as well, but remember... most of it gets sanded off anyway when you're shaping it.  

Keep sanding the body filler and applying more as you need it until it reaches a nice, smooth shape.
Use a block to do most of the sanding, so it comes out fairly even. Use your hands to sand the rounded areas and mold the edges, etc.

Once they are shaped properly, get some good automotive primer and prime them. After you prime them, sand them with some 300grit sandpaper to get it even smoother.  Probably a couple layer of primer will be needed as well to make sure it is nice and even.  After the first 2 coats of primer, move to a slightly smoother sandpaper, 380grit or so, and then the final 2 coats, use 600 grit. 

That should give you a nice smooth finish to work with just before painting them!

Hang them up and paint away!

I only worried about the front half, so you don't need to do all the detailed finishing work on the part that will be covered anyway. I used some 1/4" foam pad, from the fabric/craft store underneath the vinyl to make it soft and poofy. I cut and glued the foam pad into place, then I stretched the vinyl over it and stapled it on the back  Once the panels are done, attach them to the door panel itself using your t-nuts and your set!