no real deal, just order direct from the factory. Right now unfinished 25mm is $90 a sheet. I get emails from them and would wait till a sale happens then buy. The rolls of 1708 fiberglass- 45/45 degree weave are a SCREAMING deal at $255 for a 90 yd roll. If you try to buy it on ebay, you'll pay $10 + a yard.
for my boat project, I went in with a buddy from work who was re-doing his boat as well, together we bought quite a few panels, 3 rolls of 1708 and 2 rolls of 1.5 oz mat. Shipping was flat rate $200 to a commercial loading dock at our work.
25mm is definitely stronger than the 19mm and is overkill for a teardrop strength wise. I was thinking of using the 25mm panels because it would act as more insulation than 19mm. If one were to put 2 layers of 1708 on both sides of a 25mm 5' wide panel with no under roof supports I would expect to be able to walk across it. For my proposed 6' wide I would probably put either a 3rd layer of glass on the bottom side of the top panels or laminate strips of 19mm on the underside in strategic places and hide my electrical wiring within those strips.
the build process would be laying up panels with 2 layers of glass on the bottom side, 1 on the top, cutting to size and assembling them with strips of glass like I did for the leaning post, then putting a second layer of glass over everything on the outside.
my thought is to do the whole thing with vinylester resin, fair it and finish it off by using a hvlp gun spraying layers of gelcoat thinned with duratec. The gelcoat would need to be put on a little too thick because even with the duratec the surface will have some orange peel texture which can be wet sanded 600/800/1000 then compounded smooth.
If one were to go with epoxy I would get a different cloth without the mat on the back side as it eats up resin and doesn't add value.