wouldn't it still hit a higher top end with lower acceleration?
Yep, but only if the engines making full revs. As Dustin said, try lifting it up and briefly nailing it - see if it shifts.
I cant remember if I got my .18 to shift to 2nd with TMaxx wheels on, I do seem to remember that the 2 speed gave me issues then though. But it wasnt long til I went to the 28 and it was ok after that.