Thanks for the great answers, Wayne! Closest I have to 5mh on hand is 7. So I'll give that a try and see how she sounds. Even with the OB 167's pretty close to side and front walls, I really like the texture and imaging. Very wide and deep. Instrument placement is excellent.
On the fletcher-munson thing, I have some vintage amps and I've tried the "loudness" compensation, it does improve bass w/low levels, of course, but becomes a bit too bass heavy. I'll be the whole loudness comp thing could be better done if adjusted for room issues.