I've come to prefer 32" and 33" scales in my four string basses.
I've played 35", 34" and 33" five strings, and so long as the string tension on the B is sufficient to eliminate flab and deliver solid punch, I prefer the 33".
My good friend Andrew Drake is building me a custom five string that is a 33". He is sharing the progress of this build on the "featured builds" section in Luthiers' Corner on this forum. If you want to see progress so far the link is:
Black Limba 33 inch scale 5 string bass .
This build will be a string through and will be strung with RotoSound RS 775 LD strings. We think this combination will create the right tension to eliminate any flabbyness in the B and deliver the punch I've come to expect.
Hope this information is helpful....and I'm sure Andrew will be willing to share any secrets he might have discovered along the way in building these medium scale basses in both four and five string configurations.
Best.
Koog.