I'm not cutting into that slab.... Not happening.. I've got enough problems without asking for more... :O I wouldn't even venture a guess how the PO's installed this or what spacing the pex is at... They seemed to do everything half-cocked. Heck, look at all the houses in Levittown that were installed after WWII with no slab insulation of any kind... yah they weren't the most efficient, but they worked good too.. (Until the copper pipes broke in the concrete.. LOL) I guess it comes down to the fact that while the manual and marketing literature for this EKO say it can handle up to 35% MC, it's a deal of "yah, you can do it, but sucks to be you!" You can say that again that wood isn't for everyone... I nearly didn't go down this road and now I'm sorry I did.