I run that bar on my Longtail with a 7/8 BMX threadless stem and it really works well with that bike - wide, upright swept back and very stiff is great on a massive motorized bike with moped tires and two children aboard.
I also have one on my 80’s mountain bike and it’s great but the weight is noticeable (but doesn’t matter as much as riding position and style) as it’s actually a pretty light bike. 7/8” super wide split clamp quill stem on that bike so it works out perfectly, most bike handlebars aren’t compatible.
7/8” to 31.8 shims are pretty cheap and easy to come by but I probably would choose something lighter for high-performance riding of any sort.