I haven't have any problem with pleksy tops ( I don't realy know correctly what kind of material it is, I need to ask the guy I'm buying from), I presure test cpu block at 5 bars and there's no leaking or cracking, I can't realy see how can a top crack with ~10mm of thread if you have a little sideway force. Befor the force from a hose would crack my top, it would rip the block out of the motheboard holes, so cracking the top won't be realy a problem
