You can gain some height by putting a couple layers of boards or leveling blocks under the wheels. We had the same problem with or 1705T and decided to only chance emptying the gray tank into the tote and hold off on the black tank until we got to a dump station. I think the HiLo designers never took their designs camping.
Added Note: If you can temporarily drop the tongue some to elevate the dump valve would help.
My Great Wife Joyce
2018 Jayco Jay Flight 21QB
Formerly owned 1705T and 2310H
2012 F150 4X4 SuperCrew EcoBoost w/Leer Cap
Reese WD Strait-Line Hitch
Amateur Radio K3EXU