How to mirror fiberglass for opposite side?

Lets say I have made an elaborate fiberglass door panel. How do you mirror it to the oppisite side? Is there any trick to making the exact same thing for oppisite sides of the car? Or am I screwed and forced to endure the pain of trying to do it by ruler and eye??

I would layout the panel and take a photograph of it as straight as possible (standing over it).  Then, in photoshop or your favorite powerful image editing program, flip or mirror the image, and use that as a reference, to ease the pain of attempting to glass the otherside with identical features.I have not failed. I've just found 10,000 ways that won't work.

When you do not know what you are doing and what you are doing is the best -- that is inspiration.

Good idea I will use. Photoshop like I never knew a good use for it.

Thanks for the info. I guess I will just do two of everything when I get started in the spring. For some reason I thought that there would be an easier way to do it. ugh!!

one other thing i didn't think of until after that post - if you can get your hands on some latex (not the paint) and you make yourself a cast of your current panel, you might try pouring a thin layer of latex on the cast, let it dry - then take it off and flip it over.  you will have the  "inverted glove" of your origional, but - it will require a backing of sorts to make it useable for making your reverse cast.  you should be able to carve or form yourself a backing out of a piece of celotex or other similar insulation panels (the reason i suggest it is, it's light weight, cheap, and you can carve it with a plastic knife -though a straight razor works best in my experience).   you can get those panels in sizes at least 4" thick or down to 1.5" thick - and of course, you could stack layers to make thicker.  once you have something "roughed in" to the similar shape, you could shoot a thin layer of expanding foam (the minimum expansion type) over the whole thing, then lay your latex "flipped inside out" glove over the foam.  as the foam expands, you can press down parts that seem to be getting to high, etc.  once the thing becomes rigid, you can pour yourself some plaster, and have a permanent mold that will give you the reverse that should only take minimal fine tuning to be just what you want.  when you've got it perfected, you can take that same plaster mold, pour another thin layer of plaster in it, and press your fine tuned piece into it until it hardens.   from that cast, you can make panels that will only need to be flash sanded then they're ready for paint (unless you feel like you must put a final glaze coat over it first).  you can easily make 30+ door panels from that mold - if you're careful, who knows how many.   i've made side panels for motorcycles (with the emblem "built into" the side cover) - farings, spoilers, just about anything you can carve out of bondo, wood, plastic, whatever - get your shape you want, make a plaster cast in a plastic tub, and you're dialed and you can duplicate your work over and over.

I would suggest taking your first panel and putting tin foil on it, then glassing with about 3 layers.take it off when dry and then use the inside to mold a new one. If you want to to look good itll take time.dream it, build it, fiberglass it

I understand what you're saying, I can make molds no problem.  I was seeing if anyone's made a mirror image mold by using Superchuckles' idea or not- latex over one piece, then remove it, and flip it inside out- reinforce it, and you have a plug.  Have you done this before, or know anyone that has?  The theory is there, I just don't know how difficult or easy this really is.  Any input?