We fill up our toy hauler at Costco all the time. The location near our house isn't that busy most of the time and they have plenty of room. I see people with RVs and boats filling up there all the time as well. It's off of an interstate and is in a less populated area, so that would probably explain why there's plenty of room... there's lots of room in general out here.
I'm not sure I'd take an RV into some other locations in Denver Metro that are in more populated areas, those gas stations have way less room.... but the store in general has way less room to work with when surrounded by a city.
