I marched a couple of times using my Mack Brass euphonium. I used a harness to support the weight. I found it restricted my view of section mates to my side and I was frequently getting out of line. My teacher and section mate, Rob Stattel, used a British baritone for one of the gigs, which was lighter than his usual Willson or his backup Besson.
Dean L. Surkin
Mack Brass MACK-EU1150S, BB1 mouthpiece
Bach 36B trombone; Bach 6.5AL and Faxx 7C mouthpieces (pBone on loan to granddaughter)
Steinway 1902 Model A, restored by AC Pianocraft in 1988; Kawai MP8, Yamaha KX-76
See my avatar: Jazz (the black cockapoo; RIP) and Delilah (the cavapoo) keep me company while practicing