Didnt realize they weren't avaliable for Gen4. Ya durapro has to be big improvement.I don't think munster makes a ski bushing saver for the G4, only the ski bushing stiffener:
Similar to the Ski Bushing Savers, the Ski Bushing Stiffeners stiffen ski articulation for better ski performance. Acting as a spacer underneath the ski rubber, they remove any extra play and applies more pressure against the spindle to stabilize the ski. Compatibility: SBG01B - Skidoo Gen 4...munstercanada.com
I could see this helping, but i'm not sure how long the ski rubbers would last with it in. I'm also trying to decide between the durapro and this.