Seafoam is a good idea as a stabilizer. If you plan on starting it every once in awhile, I'd keep the tank full, not near empty. The less room for air in there the better. Several people, including myself, think its a good idea to change the oil in the Spring and in the Fall. Beyond changing the oil, Summer storage is same as a two stroke. Some fog the engine if not starting it before Winter, but that doesn't apply to your situation. I also suggest a good wash/wax and grease job, and armorall on all rubber / plastic parts. Its a good idea to go through the suspensions over the Summer and replace worn bushings / bearings / hyfax like you should do on all sleds. Yamahas seem to wear suspension components quite a bit, probably due to the increased weight.