john : i used to do fiberglass a lot for large things (and very heavy things). as long as you do 2 or more layers , its extremely stiff. i always used S type fiberglass , as thin as i could find it. if you cut away 1/8" whee the fg was going , with regular stuff you could probably get 3 or 4 layers. the thin stuff closer to 6 or 7 layers , but youre still shaping the outer one or two layers.
as long as you mix the resin and catalyst well (with a weighed ratio , not volume measured) , it dries rock hard.
theres a lot of vid's on youtube about fiberglassing speaker boxes , which was part of what i used to do. there used to be one where the guy had just gotten to the fleece stage , and he kinda half-a$$ed it , by using spray foam , but anyways , once the fleece and resin haredened , he could stand on it.
put it this way , when i wrecked my golf , the only thing that wasnt damaged , was my speaker box , and it was only 3 layers of regular fg.
very very strong stuff. ill be whipping one of these out as soon as i get something worth cutting in half...on purpose...lol..
edit: i dont know how much of a difference it makes once its all slid together , but i would probably make the top limb the removable one . if theres a reason not to , please let me know.
-hov