MSR windpro in the snow

I'm curious as to what experience people have with the MSR Windpro stove for snow camping, using it with the canister inverted. Beyond general impressions,I'd especially like to hear about:
Any comparisons of fuel usage between white gas and c canisters – i.e.,"I used to use a liter of white gas for a week of snow camping, now I use 2 canisters" or whatever the numbers are.
Anyone who has experienced what Roger Caffin has with some substance gunking up the valve.
And what means you use to hold the canister in an inverted position.
Thanks!