What i do if i am not going to finish the song in RB, is to build the song in BiaB, then export all the Rt and Rd tracks as wave files and then save the rest as a midi file and open that in Sonar, and import the individual wave as well. This works great for me.

One thing you can do is to try processing the song inside RB, it will use many of the same plugins as Sonar, since both were originally DX based, they can share quite nicely

HP Win 11 12 gig ram, Mac mini with 16 gig of ram, BiaB 2025, Realband, Reaper 7, Harrison Mixbus 9 32c , Melodyne 5 editor, Presonus Audiobox 1818VSL, Presonus control app.