small polyethylene boatbuilding

[gesdim]

Hi all,
I call about dilemma between steel or polyethylene boat building; I want to build about 8' long dinghies, and about 60 lb(P.E.) or 80lb (steel) weight;
boat usage will be in summer time (about 3 months), on big mountain lake, there are mostly gravel and stone beach, with possible sudden weave; most usually local boat are rivet steel boat, smaller from 8' to 10', bigger to 21', manufactured in local tinman workshops ; local polyester boat factory produce only expensive 13' open boat and bigger. I plane to build polyethylene boat similar as rigid inflatable boat, (welding method with special electric dryer and electrode), from polyethylene tube (diameter 10")(chambers), polyethylene plate 1/4"(hull) and p.e. plate ~1/2" (stern), of course with necessary ribs . Polyethylene boat is safe, without needful maintenance, maybe only keeping can be problematic ( resistance from low temperature (surface freezing), or from high temperature in summer (locally softened); same, polyethylene boat can't be sink in the water (because winter keeping ).
regards from lake Ohrid, Macedonia, Europe