I’m 5’7″, 130lbs and have loved the OTK product ever since I tried it. I always had an issue with weight-jacking too. I’ve never had a kart react like the Tony Kart does.
And the myth that they fall off is just that, a myth. I’ve cited these examples many times, but there are plenty of results to deny that myth. Ashley Rogero won lots of big races on a Tony that was a few seasons old. Tommy Andersen set fast lap and won one of the heats in TaG Senior at SuperNationals a few years ago on a Kosmic that was a couple seasons old. Stepanova Nekeel bought some used Tony for like $950 AT the Rotax Grands that weekend and went out and won Rotax Senior.