Well, I started riding on RM80 in friend's backyard when I was only 4'11". It has seat 4" higher than Ninja 250. So I figured that was normal having seat around my neck level!
I learned to ride bikes that way. Never gave me any troubles how tall they were. Riding horses also helped with controlling bikes.
I also like getting air on my bikes, so having as much ground clearance as possible helps prevent damage when landing.
Some tips:
https://www.youtube.com/watch?v=4IMtZzrsfAQ
https://www.youtube.com/watch?v=etqqzJ06R90