After upgrading to Crossover 20:
My previous working version of FL Studio 20-32 (installed into a Win 7 - 32 bottle, using the FL Studio 11 Crosstie) runs as before the Crossover upgrade.
Installed and tested the latest build: FL20.7.3.1987 in a new Win10 - 64 bottle, using the Fl Studio 20 Crosstie (Deselected ASIO-FOR-ALL in the installer). I am VERY impressed with how well this performs. The Default 64 bit version of FL Studio installs and runs very well. Bridging 32-bit VST's still appears to be problematic. As before, the program complains about being run in administrator mode and FL-Studio pop-up dialogs (for naming items, searching the database, etc) will not allow backspacing - probably has to do with key bindings and context in the program UI.