Hi Smitty --
Try to get up with Paul Dalleska at the Huck or Marty, his predecessor there. The Huck has loops at each end on which they turn their entire train.
One can certainly build a loop with a 24 degree curve, but whether you could turn a whole train on it without difficulty is another question. A curve that sharp would mean lots of flange wear and rail wear, even if lubricated. My advice would be to make the curve as wide as possible based on the amount of land available. The wide gauge railroads don't care for anything much tighter than 12 degrees.
Cheers -- Wayne