Dear Mary:
Note that RMS / RiverCAD uses HEC-RAS version 2.2.1 FORTRAN analysis engine. There are some "problems" with the 3.0.1 engine, so we are waiting for the next released engine to support. There are some differences in the 2 analysis engine outputs, and that is probably what you are running into.
I would suspect that if you were to import your RMS model into the US Army Corps of Engineers HEC-RAS version 2.2 software that the results would match perfectly.
Sincerely,
Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com