I did it with tanks on and all is well. There's probably someone that did it with tanks off and they'll tell u it came out fine too. But I'll leave that for them. Seems more intuitive to have the tanks on for the final assembly. but I don't see/know the circumstances u are dealing with.
RV 7A. RV #9700
Built in SoCal KCCB
Phase 1 Completed Nov 2017
120 Hours in Year 1 & 3x cross the USA