without reading other comments yet:
LOVE IT! Real authentic ol' timey. And very good playing, mix, intonation/tuning on the instruments.
Two things would put it over the top...I listen to a lot of B'grass...my latest 'jag'.
1-There was most often an obligatory measure or two extra on the one chord before the change to the four...or an extra measure or two on the five chord just before the turnaround...or at the end of the turnaround. Seems almost universal among the recording artists of the period. Something borrowed from classical and/or keltic, I think.
2-The bass is pretty fat-sounding, compared to most like recordings I hear. A little more string and less lower-mid moo? And it would break thing up real nice if the bass part played the eigth-note triplet time once in a while instead of the steady quarters [assuming 6/8 time]...leading up to chord changes in the progression.....also a stock thing among the better practitioners...from what I hear.
Really dig the sound of the mando....real woody....sounds real old and expensive. I use a brand-X Fender mando with a plywood top. Can't touch your sound on that. If you're using a plywood mando...please tell me how you can get that sound!
That's a fine piece of art you made. A little 'record scratch', and it's ready for a History Channel soundtrack....or a contract with a label specializing in either Gospel or American Trad Bluegrass/Country. That good.