Any holes you attempt to "Repair" with fiberglass product are going to lead to huge. messy repairs as well as a major painting
My usual approach is to "repurpose" the hole or hide it as something else. There are several sizes of round and square vents at the RV store that may help. You could always point out that they are vents for a stuffy closet etc. If the holes are real big, a set of speaker covers might also do the trick.
In spite of what others may chime in with, "invisible" (meaning it's as if it was never there) fiberglass repair on flat areas can be very difficult, messy and time consuming.
I only base this suggestion based on having been doing fiberglass repair since my first Corvette in 1964.
For the smaller holes, screws with button covers, as used all over the outside of Scamps, work well. And a square light
woul d look fine on that square hole.
In repairing FGRV's, restoration as original doesn't really count that much, if at all.