Good day!
When it snows here we use 1/4" coroplast/signboard for ski's (spad). For your size cut a piece 2" wide by 20" long. Crease the front of the coro and insert a bent coat hangar to form the front of the ski. Cut a small piece of 1/8" ply 3"x3" with a hole for the landing gear and stick (and glue) the ply down in the flutes midway of the ski. Take the remaining coat hangar and insert one end into a one of the flutes and bend the other up and tape it to the landing gear. Ive got a pic but havent the faintest how to attach it. It's of my Ghetto Bird. I could email you a pic if you want. If you are just learning, the ski's may throw a whole new airfoil (at least mine do) to the situation. Something to think about.

Spanky