For quite a while, the outer larger branches of Jupiter sousaphones are quite thick, but the inner ones (beginning with #3, which is the one that rests on one's shoulder) are thin. (That having been said, the King sousaphones have been quite thin for quite a long time.) When they hang the Jupiters or Kings on things that aren't really designed for hanging sousaphones, the branch that sits on the player's shoulder ends up being caved in, and I have to fix those back round again. I'm pretty good at it, as I have to do it so often. The bells are thick (enough) these days. The old Jupiter valves (that would collect brass oxide from the casings) were otherwise trouble-free, but what I think I've observed is that - now that they've changed the way they build the pistons - I'm thinking that they also tightened up the tolerances but without stepping up the fit... so now I have to repair quite a few casings.
A long time Jupiter problem - which continues on into the present - is that the brace flanges are (in my opinion) too thin, as well as the tension ring for the neck receiver being made out of sheet metal instead of something thicker. The Jupiter pot metal water keys are annoying, because when they break they are not repairable. Another really annoying thing with Jupiter sousaphones is the body elbow brace system, which is quite fragile and annoyingly troublesome to repair or replace.
For an economy sousaphone, the Jupiter price is pretty fancy, in my view.
JP sousaphones (and I'm biased, because I sell them) feature much nicer valves and slides, and I can beat Jupiter prices by thousands of dollars. JP sousaphones have one Achilles heel. It is that the ring that braces the lower mouthpipe isn't as tough as the one on the genuine King, but - of course - this would never break would students loosen the tension screw when inserting and removing the neck...
JP sousaphones are a pound or two heavier than (new) King, and the sheet metal of the branches is a bit thicker than King. Again, JP sousaphone valve sets are really well made. Of course they're only three valves, but they're good enough (quality-wise) to put on a professional use frankentuba and to be proud of the valves and slides.
