I've got the same inseam as you, it can be a bit of an issue but only when trying to paddle it out of a parking space or sometimes balancing it when 2 up, but never dumped it. Easy fixes are shorter shock and lowering the fork tubes, thicker soles.
In terms of only riding one-up, would you say that you feel confident sustaining the bike at a red light for example? I've heard that inclines and backing out of space is a bit on the strenuous side, but I wouldn't mind pulling the bike out being off of it. I would love to sit on one and really get a feel for the seat height, but not many get listed locally near me. If I were to test one, it would be quite a distance from me. Without being a bother, could you give your thoughts on these questions?
1. Do you balance the bike one your toes/balls of your feet, or one foot it?
2. Based on 1, how confident do you feel handling the bike?
3. Is the weight on the K100 "comfortably" manageable? The heaviest motorcycle I've ridden is a 2013 Honda Shadow Phantom (550 lbs), and while it felt heavy, I didn't feel uncomfortable or scared of dumping it at all.
Thanks for your feedback, I value it immensely!
Seb