Identifying My Boondock for Correct T@B 320 Cover

They’re all the same dimensions, at least through 2020 (not sure about 2021). The Outback is the same model as your 2018 Boondock. For 2019 (and 2020, I think), they split the model into Lite and Edge versions. The Lite lacks the rear rack, full size spare, and the grey Marmoleum flooring of yours, the Edge added a front light bar and rear spotlights.

I called NuCamp and asked if there was any problem with using a Costco tarp. They said absolutely none. Costco tarps are cheap and heavy weight. We tie a 3' piece of rope to each corner and then my wife and I "sail" it over the back, over the rack, over the roof vent and all the way to the front. Tie it down and we're good.  Cheap, sturdy, easy.

I do the same on my TAB 400. Costco tarp brown side down. Leaves plenty of ventilation, fits from handles to handles, and for a two pack for $20 you can replace them annually. I park mine on the side of a house under trees and it is essentially for keeping leaves off the top.