When you dream, dream big! Thinking of your hangar clearance? If you can get enough height to the top of the prop arc, plus a foot or so, you can taxi into the hangar....adds flying time to your day not having to push, pull or otherwise maneuver your airplane after you leave the cockpit.
Otherwise, I don't persoally have an idea or way to measure the Top Cub. Cub Crafters phone number is: 509-248-9491
Tail height info is available on Wipaire's website under Customer Service/FAQ's . According to that info the tail height of PA-18 on 2100 Amphibs is about 10'-2".