I had one of these jacks back in the '70s. Used it on a Champion 18' stickie and only had to use it once. It did the job. I let it go with the Champion back in about '84.
The only problem I see is that most
fiberglass trailers use a square torflex type axle instead of a round axle with springs. I don't know how this jack would act when trying to make it's way around a square tube.
73
Orlen