i know that most of us hate to think about roof penetrations. However, a piece of 3/4" PVC conduit penetrating the roof and sticking up maybe 1/4", well sealed, and then a PVC combiner box with a hole for the conduit to go through it and heavily sealed to the roof will never leak. Dicor and sealastic will totally seal things. In addition, a small 1/8" weep hole in the side of the combiner box at the bottom of the low side will take care of any seal leakage as well. When you put the combiner box down over the conduit, liberally butter it with sealastic and clean up the edges. water takes the easy way...not the hard way.