I was an amateur musician for about 35 years and spent time studying guitar, then piano, sax, and finally viola. As time went on, I became more serious and systematic about it, so that by the time I got to viola I was doing a weekly lesson, working daily on a scale, an etude, and a piece, generally practicing at least an hour every day, although with some days off. I love jazz, but after about 15 years of trying on sax I decided that I was never going to be the kind of jazz improviser that anyone would voluntarily listen to. I've always loved the cello, and especially the Bach cello suites. I did viola instead only because there was no cello teacher locally available. On viola, I got good enough that after practicing for several months I was able to play competently through the Brahms E minor symphony with a community orchestra. That was a huge rush, with a major feeling of accomplishment. However, that group usually only allowed a few weeks to work on material, so when they were like, "OK, we're doing Firebird next month," I just couldn't hack it. I was in a quartet that just played at our own houses, but that group broke up, partly because the first violin was flaky and partly because I wasn't very good. I got discouraged after all these experiences and gave up music completely about five years ago. I would have been happy to have an opportunity to play with other adults in some context that was well matched to my level of ability and aptitude, but those opportunities seemed impossible to find.
Taking stock of all this, I'm now thinking that maybe it would make sense to try double bass. The advantages would be:-- Bassists are always in demand for both jazz and classical, also maybe rockabilly. In a jazz context, playing good solos is not as mandatory for a bass player as for a horn player. I have experience playing viola, so I'm not afraid of strings and am fairly confident of my ability to play in tune.
My big doubt is that I don't have a good feeling for whether my physical size is an issue. I'm 5'6" and my hands are probably about average size for a male of my height. On sax, I was mainly a tenor player, and when I tried bari I found that the instrument was just too big and heavy to be practical for me. On viola, a lot of the left-hand stretches were somewhat difficult for me.
I've never even held a double bass, so I have no clue about what it's like physically. Well, at least you aren't holding the damn thing on a neck strap like a baritone sax! How important are body size and hand size for this instrument? Er, please don't reply with the high-school guidance counselor type of stuff like, "A guy with only one leg climbed Mount Everest." I'm looking to maximize my chances, not make a miracle story suitable for an inspirational speaking tour.