I have a rear queeen slide KZ and in the ten years I've had it camping in all weather it has not leaked. I also do not consider it cold back there but do use matress pad heaters when the temps drop below freezing.
All things equal I'd would if I did it again bypass this option and just go straight to a TT with walk around bed.
The unit has been decent but I've never been over the moon about it. When pushed back into the rig that whole area is not accessable including getting to the witerizing valve on the water heater, no access to the sofa or dinnette while on the road either which has proven to be a real PITA. I knew all this before purchasing but got it because DW was sold on the part where it fit in the driveway.
