I'm happy with the performance of OS 3.9 on this 50mhz 030. Might be neat to sneak the VXL inside my A500 sometime and have 3.9 running on that, but am afraid its stock power supply would be too wimpy for it.
I had the same setup on my A500+, 50MHz/8MB upgraded VXL running 3.9 from an external SupraDrive, all running on the same stock A500 PSU. Can't recall any cap clearance issues, though I probably would've just shoved it over as far as it'd go.