You can use any size 3s you want upto and including 5000mah as long as it is above 25c. The problem is mounting it and weight. You may find 2 batteries are the better option. I use dual batts running a stock 2200mah under the belly and a 2250mah turnigy nanotech in the shell. That gives me 13 mins useful flight time from start of motors to landing.
You may find a 5000mah gives you similar but it'll be a right fatty and leave you little room for FPV kit (if you choose to go that way). You will have to find a way to mount that in the shell which has its own challenges.
What weight/size is the batt you have in mind?