I've tried the single ply, I've done tests on about 7 different brands of TP. I'm going to say this.. The LITTLE effort it takes to dump and clean a black water tank. We now use the TP that our rear-ends like. We have gone as far as 2 weeks without dumping. When it came time to dump, NO ISSUES!! We do use a chemical for odor control, but beyond that.. I use the TP I want to use.
my 2 cents
2000 Jayco Eagle 269 RD Fifth wheel
2002 Chevrolet ECSB Z71 Pickup (DD and short haul tow vehicle)
1988 Chevrolet Crew Cab Dually (long haul tow vehicle)