It's going to depend a lot on how heavy your foot is, but I would guess 10+, possibly 11-12.
The BT Cruiser is a popular and well liked small coach. Gulfstream in general has a mixed reputation, with some folks saying "never again" and others loving their Gulfstreams. My impression is that the smaller Gulfstreams have a better rep than the mid-range Class A's, but that's based on what I see and hear online, not personal experience.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL