I am running a castle sidewinder sct setup. I was thinking about trying a 2200mah lipo. How much run time do you think I would get? Our heats are 5 min with a 10 min main.

Depends on motor, driving style, track size, gearing. In general youd prolly make the quals, but most likely not the mains.

Don't forget, mah & c rating work together to provide amps available. If that 2200mah pack is a 30c then you only have 66a available. You might make it on runtime but not have the power when you want it.