All of my night training for PPL-H was in an R22. I noticed no particular challenges maintaining stability at night. You either have a sufficient horizon or you don't. If you don't then you are not VFR
If you start getting into questions about how much of a horizon you have, or needing "a good panel fit", then perhaps it is time to file IFR
YMMV, personal minimums and all that sort of thing...