Dave,
I went into RR-Track and created this diagram using the components available.
The two Korber roundhouses have the same width front panels. The narrower the stall arc the farther the RH front is from the center of the TT. The TT diameter is immaterial. The TT diameter only affects the total distance needed. The difference in total length/space needed between a 34" TT/RH and a 28" TT/RH is 3".
Jan