I'm getting new boots, the Lange World Cup RP, Lange's plug model, and am interested in getting Zipfit liners with them. I'm looking at the Zipfit World Cup model which I can get at a decent price, but am concerned about the fit with the RP shell. The Zipfit website says they're made for low volume plug/race shells, but are they much thicker than the next model Gara? I've also read that some material can be removed from inside the liners to make them thinner at certain places if needed; could this be considered if the World Cup liners are a bit too thick to fit in the RP shell? So I'm just wondering if any of you have had experience with the Zipfit World Cup liners and plug shells.