I don't eat white rice either (unless it's an emergency and I just HAVE to get a meal ready quickly, it cooks faster), I only use brown rice, because my sweet husband has high cholesterol and should not eat high glycemic index foods...
When I started the BTC diet (or something like it, I didn't know it was called that at the time, I was just listenning to my best friends advice, who has UC), I didn't notice an increase in C. I think because I was eating less things that would make it to my colon (less fiber and other things that bother us) I just had less material there and din't have to gooften anyway. That reduced the problem, though, because I had less stuff in my system.
If you're in pain, it's probably too much IF. It's always a balance between IF and no C... At least with me. Before, I would eat a TON of fiber and for a while I didn't even have C (I have had C since I was born)... but I didn't have pain back then (or I wasn't noticing it ) so I didn't even think I was doing something bad...