I have not marched with 2141, but my advice would be to have a horizontal hook fitted onto the bottom bow and use a harness to carry, as per discussion in recent thread. Lyre blocks can be obtained which fit around the tuning slide (I think sold for trombones?) to avoid having to solder onto the front.
With those fitting, I can't see you having a problem. I march with PT-20 suitably equipped.
As for lyres on tubas not outfitted for marching I have seen a photo of Swedish female military tubist using a trombone lyre of the type attached to the receiver on her Yamaha 621 tuba.
I really wonder WHY you would even consider marching with such an instrument. From personal experience as well as a lot of observation I advise strongly against the idea as marching gigs are the time and place where you are most likely to do some serious damage to the instrument. Get some old Boosey Imperial or some such and keep your good axe in one piece.