Charlie, I haven't been in a thundercat, but if you're just casting off the middle of the deck and keeping your centre of gravity low then it shouldn't be a problem. I put a high casting deck on the bow of our 14' stabi. It can be a bit dicey in a choppy sea or when a boat wake is going past, but that's just because of the high position up front. Standing and casting from the deck at the back of the boat is easy.

A bum bar would make my casting deck far more usable, but I haven't quite figured out how to fit one yet. They cop a bit of punishment and need to be very well secured. You might want to look at whether or not a bum bar can be fitted on the thundercat.

Hopefully someone who owns one will reply

Ask him if a water test is possible, you'll find the answer straight away.