In some of the older threads I’ve seen mention of making a unicycle with a coaster brake hub. The most recent is from Sam Goodburn who seemed to think it was easier than a freewheel. It’s been a long time since I rode a bike with a coaster brake so I’m having difficulty picturing what it would be like on a unicycle. However, it seems like you’d be able to activate the brake in the power position (one foot down) so it might be worth a try. There’s a possibility of accidental braking since there’s some slight backward pedal movement during balancing and there’s a benefit to modulating the braking. However, having to move a hand to the brake makes it harder to balance so removing the need for this would be a benefit. I haven’t mastered going back and forth between riding and braking yet. I’m dubious about a larger wheel but I’m still planning to try out 24". I’d like to get a Huni-Rex and make that a freewheel. The lower pedal position would be a benefit. I’m not sure I’d ever want to ride around cars, though. I’ve ridden a little offroad and it’s fun but I need more practice. Thanks for the tips on a brake!