One thing I found the hard way doing a WDH myself was that the standard shank with the Pro Series RB2 did not give me enough drop for my Yukon. Ordered one yet it was too long and would drag; waiting for another. Part of the confusion was from watching a video that showed you how to measure, but an important calculation- the top of the coupler height is provided by ETI. For the 19 & 21 Dennis told me it was 20". The standard shank for the E2 doesn't look like it gives much drop either. That is one thing about ETI- they have an assortment of shanks to use.
Haven't heard of Lazydays RV before; anyone have experience?