i dunno man... i sometimes wear cobras for alpine... i take off the heel at belays and dont really have a problem... even climbing a dozen or more pitches isn't too bad... i think sizing is important more than anything else... sizing 2 sizes too small is just dumb... doesn't really help anyways... i find that if you have strong feet, you can wear slippers all day in cracks no prob... though rattly fist cracks will always hurt...