My first Grumman, a 1977 Cheetah, N9988U, had the fiberglass ramps. Oil and time had degraded the fiberglass until it sagged down almost totally closing the exit area. This is true with all of the '75 through '77 exit ramps. I had two exit ramps made out of fiberglass that matched the originals.  They were made so they'd never sag.  WAAAAY overkill.

Note: Grummans after 1997 have metal ramps that do not flow as well as the fiberglass ramps.
. . . . .Plus, they are prone to cracking and causing the cowling to crack.