I didn't realize the plane in question was an open frame. I defiinitely wouldn't even think about going through the trouble involved in fiberglassing it.
The iron on fabric coverings are very easy to use and work great. Worldtex, Colortex, etc. I don't think Colortex is available any more but it's exactly the same as Worldtex. It needs to be sealed to prevent stains and dirt from getting into the fabric. Clear paint or any type of butyrate dope is good.
The BUSA EAA bipe below is covered with iron on Colortex and painted with dope, brushed on.