If you're talking about a low-B setup I think the longer string length may be beneficial to get that low fundamental. Keep in mind the string length of a 3/4 size upright is over 40". A high-C setup might make more sense as a short scale, more of a bass "guitar". Just my opinion.
Jimmy J
Agree about the longer scale length generally being better suited to a B-string. But... it is interesting to note that Alembic made three Series II six-string basses for Phil Lesh a number of years ago. When he ordered the first one he wanted a short-scale bass and Mica kind of talked him out of it thinking short-scale would not give him the kind of B-string response he would be happy with. Alembic made him a medium scale Balance K Series II six-string. He subsequently ordered a similar six-string Series II but this time as short-scale. Mica was surprised at how good the response on the B-string was and Phil was happy enough with it to order a third six-string, once again short-scale. He has been playing the short-scale basses for about ten years now, not sure how often he plays the medium scale. Since he used short-scale basses for many years in the 60s and 70s Phil was happy to return to short-scale because of the ease of playing for him due to years of short-scale muscle memory.
IMO one con to a five-string Stanley bass is the body shape which lends itself to a certain amount of neck-dive, the extra weight at the headstock for the fifth string tuning key would make it worse. It is actually pretty amazing that Stanley can play a short-scale instrument due to his rather large hands but obviously it works for him. There is no one-size fits all approach at Alembic and that is one of the strengths of the company... they can make whatever works for the individual player, especially if you ask nicely