Hey Bro, if I were in your position (which I was at one time) I would just work with the existing inner and outer door skins that came with the car, keep in mind it's just fiberglass, they can be modified, repaired, and molded to alignment. Adding more fiberglass or marglass (aka kitty hair), and or bondo putty won't make that much more difference in weight.
You may possibly face more problems buying other door skins that won't match and even harder to modify and wasted $$ just my .02 cents