I did something similar for our 30' Sabre. So far, so great! Holding up very well, and we get some crazy winds here in coastal Maine frequently.
Frame (PVC & 2x4s for posts) cost all of about $60-$70, plus a 20'x40' heavy duty green tarp (about $70, which is holding up well, and I hope to use it next year).
I figure, it'll take about an hour in the spring and fall to build and tear down each year...not bad. It's tall enough inside to walk around inside, plus holds some heat when I string up work lights.
Nice thing is, snow slides right off with just a tap from a roof rake. Boat is in our driveway, so it's easy and convenient to check on her, and keep snow off.
