You might want to switch to a shorter prop, but try not to make too drastic of a change. Your plane will behave much differently with the skis alone, much less making major changes elsewhere. There was a review of skis in RC Report(the best rc mag by the way) a couple of issues ago. They compared the Maiden Model skis to the DuBro's. The Maiden Model's are a little more expensive, but the one big advantage that they have is a higher mounting block. They would be better in your situation, it would give you a little more prop clearance. If I remember correctly, I was chopping snow with my prop til I got up to speed, and the skis came up out of the snow. I think skis would work better on hard packed snow rather than powdery snow. I have seen several guys fly off of snow using floats, and this seems to work really well. Powdery snow isn't an issue with floats. Anyway if you want to check out the Maiden Model skis go to
http://www.maidenusammp.com/.
The other issue that I had with the dubros, was that the nose ski on my trainer wanted to flex up into the prop. I was able to abjust it though without too much trouble.
Good luck on whichever ones you go with. Don't ever let a little snow keep you from flying.
Allan
P.S. I am in no way affiliated with Maiden Models, or RC Report magazine.