If you proforma, you will be warned that you will wipe out the new proforma file. This issue is not new. The very short window to get everything done shows. I seldom do a proforma during the tax year. I try to wait and do it in the processing year, that way hopefully all of the bugs are fixed.

Pick one client you know is a mess. Do a new proforma and see how it works for that one client. IF AOK, then do the others. 

Good Luck