RE: Looking for a good first sailplane
EPP is super tough, no doubt about it, but it tends to be heavy.
I love EPP for my slope planes, but for a thermal plane, I think Multiplex has hit the right balance with the Elapor Easy Glider. Not as heavy or rubbery as EPP. Not as brittle or light as as EPS. It is right in the middle. They seem to have the airfoil right too.
25 oz all up on a 1.8 meter wing works well.