Just thought I'd give a little update since I put the hot water to the pex. I am running my boiler at 180 HL with 160 LL. I had all the loops hung up nicely to the ceiling joists with hangers about every other one. Well this stuff is like rubber with heat to it. Had to go back and nail it up on every joist to make it stay up on the ceiling. The pex-a I ran for domestic hot water is much less flexable , but only 130 max temp too.