I will either return this unit or put it together as a 4 tray set-up for family trips and buy a 1-up as my daily driver. Still deciding.
I've had the same frustration as Steve Brain (below) putting together the original rack. Furthermore, I just got the add-on and am again frustrated that assembly will be a painful process. You have to remove one of the trays on the NV standard rack in order to put the add-on in. Then reassemble the rest of the trays afterward. I purchased the add-on so I could ""throw it on" in a pinch when I need to haul two bikes, but had no intention of keeping it on the entire time. I wrongly assumed it would be a quick take on/off. Boy was I wrong. I wish their mfg. specs were tighter so the bolts installed easier and also wish they would design the add-on with the mentality that people want to use it occasionally, but don't want to leave it permanently on. The rack is too large and heavy with 4 trays as a daily user. All that said, the rack performs amazingly once its together. Right now I'm debating whether to keep the add-on and keep together permanently as a 4 bike setup and then buy a 1-up or something smaller/lighter for my daily driving rack. The NV would sit in the garage until the big family trips. Would hate to do this, but painful assembly leaves little choice.