If you stitch 2mm or above leather in the proper saddle stitch and awl way, and especially if you use waxed linen to do so, I can assure you from experience that a pony and/or a saddler's clam will save you great deal of major grief with your hands later in life; I've done a lot of harness fitting and modification for years, and when I was younger I poo-pood the use of them and although I felt no ill effects at the time I have this year had three lots of surgery on my hands and have been unable to do anything at all; pretty much no crafts or tool work for twelve months and another twelve to go 'till they're mended; It has not been fun, to say the least! The consultant who did the surgery was in no doubt at all as to what had caused the problem.
Obviously it depends on how much of this you're going to do, but for the minimal time and money it takes to make something up itb doesn't make sense not to try it out at least. I'm a firm believer in encouraging people to think about the consequences of working with their hands, and believe there are real benefits to be had from taking precautions to alleviate
problems that may not become apparent until later in life - I certainly wish I'd taken the advice I was given by men and women who could see what I was potentially doing to myself, but I knew better :-(................