I did mine once wakeboarding. X4 on the Helmet. I use a Bern Macnon H20. LOVE IT! I may look like an old fool, but I will be able to continue to progress and wont have any eardrum problems. I know skiing is bit different and some will argue the more surface area because of the speed "may" cause neck injury. I have yet to run into someone who has been hurt because of wearing a helmet. However in this thread alone we already have 5 or 6 that took eardrum poundings without it.
I would think el cheapo foam one would either jam in more or fly out. Go the custom route I use custom ones for shooting and ops. Worth every penny.
CURRENT: 2008 SANTE 210
2000 Mastercraft Xstar
2004,2005 Ski Centurion Avalanche C4
2003, Ski Centurion Cyclone
99,2000,2001, 2002 Ski Centurion Elite V/Hurricane/lightning
88 2001 Nautique