I have some fiberglass/foam composite panels and some aluminum pieces. On either one, I have used "sidewalk bolts" and "clip nuts" to attach them.
Attachment:
Body fasteners.jpg
A piece of angle with a nice big hole in it riveted to the frame or an "extension" (piece of aluminum tube) works with a clip nut. The nut clips into the hole (Hmmm... Is that why they call 'em clip nuts???) and provides a rather solid mount with some wiggle room. The big flat head "bolt" (Looks like a screw to me...) goes through the panel. That wide head spreads the load, doesn't protrude much. You can paint 'em if you like, but they're not gonna be invisible. Mine is a track car, not a beauty queen to begin with, so I didn't worry about it. Your mileage might vary...
There's also "Terry Spring" latches which are popular with the sports-racer crowd. I don't have a picture, but you can google 'em up for a look-see. Seems like I got mine from Pegasus.
Another option is the "Slidey Latch"... Sorry, don't remember the right name... I used them on the panel beside the driver that covers battery, fuel cell and such. They look like this:
Attachment:
7 13 13 Slidey Catch.jpg
Again, not invisible, but they're easy to open/close and rather small.
Last, but not least, the ol' "Draw Latch" from your local hardware store. Cheap, easy to find, easy to mount, not invisible worth a damn, and subject to criticism from people who have never built a model car, much less a real one... "Hey, that looks like the latch on my tool box!" "It might be, you better go look at your tool box"...
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Draw Latch.jpg
And that's my .02... For you, No Charge!
JDK
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JD, father of
Quinn, Son of a...
Build LogQuinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special "Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom