So I'm looking to get second set of rims and tires for the rear of my 16SE 700R now its all stock but how big of tire can I fit on this beast.

 

What paddle pattern are you looking at?

 

Sorry to put this in two post but it will not let me edit my other one. I'm not sure if you are new to paddles but something you need to keep in mind is the style of paddle. If you are looking for straight line power something like the Skat-Trak Hauler is a great tire, but it doesn't turn as well as others. If you are looking for something that turns better you need angled paddles. If you take a look at their website it can get you started in the right direction.
Skat-Trak