On MBP5,2, following the success of graphics acceleration made possible again by
@ASentientBot , I've made BS my principal macOS now.
I'm prudent and use rsyncs to keep user data in sync both ways between Catalina and BS. Note that the scripts are run on BS because BS data is not seen properly from Catalina, at least for the OCLP installation. This in addition to the usual backup methods.
I have three installations now on different SSDs (all are Samsung 860 EVO or 840, 500GB):
1- Catalina 10.15.7 (19H1030) on an SSD now connected to USB. Graphics acceleration with ASentientBot's Catalina SkyLight framework etc.
2- BigSur 11.3 (20E232) on an SSD which is now on internal SATA. Installed with OCLP 0.1.1 including system volume patching. Graphics acceleration with ASentientBot's public beta BS SkyLight framework etc.
3- BigSur 11.4beta1 (20F5046g) on an SSD which is connected to USB. Installed with jackluke's BigSurBasesystemfix and OC 4b.
I'm quite happy with this setup, and I'm convinced now that BS can be used in production on MBP5,2 (which has Nvidia Geforce 9400M and 9600M GT GPUs).
ad 2: just lacking keyboard backlight.
ad 3: keyboard backlight in place. Of course I'd be happy to have support for graphics acceleration also with this installation method.
Great thanks again to ASentientBot, to khronokernel and the OCLP team, to jackluke, and to dodsude1!
I'll continue BS installation exercises in verbose mode to disks on SATA and USB to find out about the occasional hangs observed during installation using OCLP.
EDIT: to my knowledge BigSurBasesystemfix is the only installation method which works without any hickups right now on Legacy USB machines, like MBP5,2 is.