have you called your local tracks?
if they are not roar then you most likely can race with the .26 that comes in the ultra mbx pro.

i used to have no problems at all driving my mbx pro on the track and kept up with kyoshos and the like. (track bashing, no official races)
it really comes down to the driver.

i would though suggest that you upgrade to the 200 oz servo for steering that airtronics makes, you can get it for a damn good orice through nitrohouse.com

that alone will help you on the track considerably.

i have now retired the ultra mbx pro and am using my hopped up hyper 7 with all pcr parts. it is fast and very responsive but in reality i had just about the same amount of fun on the track with the ultra mbx pro.