broke mine in march 04 - 2x breaks - one just below ball, and again about 3" down (arm in 3 parts). my ortho used a nice titanium rod and screw to stabilize mine. was to have no splint after surgery (just a sling) but the bone split out at bottom of rod and he was concerned that a good bump would break below the rod and would have to remove and start over. the choice to use the rod over just a cast was that there is less shoulder/elbow immobilazation - thus, less chance for having a frozen shoulder or elbow. 8-weeks with cast w/o any movement versus 2-weeks in splint w/o movement if use rod.
after surgery for week had only sling (then he noticed the split below the rod) - i then started with a splint for 2-weeks (plastic thing on back/bottom of arm in L shape with ace bandages holding it on). i then had it on for another week with occasional removal to do some exercises and then as needed when going out to protect for 2 more weeks. total of 5 weeks messing with hard splint in some manner. (could remove to shower after first 2 weeks - ahhh)
why would he use an "upper body cast" as opposed to a sling? perhaps you got the term wrong?? ask about a splint versus a cast and if can be removed to do some motion exercises.
i liked the hard splint versus a cast as it was lighter (as one sided cast) and i felt that my arm was still protected. i still had to use a sling with this as it kept the weight of my arm from stretching (stressing) the shoulder and rotator cuff. also i could not hold my arm up for the first few weeks.
i did about 3 months of physical therapy 3x per week. also did same exercises at home on non-pt days (recommended). still exercising for range of motion and lifting weights.
there are times now that i don't think about or feel the result of the break however there is still daily muscle pain and the shoulder muscles have not yet fully tightened. i started casually riding after about 5-months on my play-bike, after 6-months i was back riding the crf450. note that i still don't have full strength and i am taking it easy (i don't make my living riding so there is no pressure that i go fast or high ever!)
range of motion (rom) in elbow at 5-weeks was about 80%, it is now 100%. rom in wrist was about 80% at 5-weeks, it is 100% now. rom shoulder at 5-weeks was about 45% - could not get straight out from body yet (moving with other arm - could not do with own strength), rom in shoulder is now about 95% under own strength - using a weight it is about 97%. note that the loss of rom was due to the immobilization in the splint. prior to the splint i had 100% in elbow and wrist (who knows about shoulder as i could not move at all)
good luck and don't rush the recovery - you really tear things up when this happens and you have to give the bones and muscles time to heal. nice thing is the bones heal stronger than before...