I've used a lavacore on and off for 4 years now and I don't think I've ever had that problem. When I don't need more warmth than the lavacore can provide, it's my go to exposure protection. When I do, neoprene shorty+lavacore still beats a thicker full wetsuit by a country mile. I've also used my lavacore as a drysuit undergarment many times with good results.they get baggy when under water. This is no no as it not only adds drag but also interfere with normal buoyancy control.
Frogskin sounds interesting. After hearing similar claims about sharkskin I think I will reserve judgement for now. Those turned out to be BS since (as you accurately noted) sharkskin and lavacore are virtually identical.
When Frogskin starts showing up in dive shops, I'll definitely check one out. I don't think I'll be importing them myself before then.