I'm 6'1 and my bars are 20 high I think... My back only hurts if I ride for long distances or times. I would raise them but I cut my t-tube, it's kinda only just in the steertube already.
If you cut a groove along the edge of the ridge on the t-tube with a hacksaw it gives it room to flex and get tighter. I did this to reinforce my 08 fork.
Every time you find yourself not trying anything at the skatepark, throw a barspin. I just whored barspins for like a week until I landed them, then I just kept doing them flat at the park in between lines, now I do them IN the lines lol.
My yard is on a kinda slope, theres a 2 foot drop from the front verandah, a 4 foot high wheelchair ramp to the back verandah, and some 1 foot high ledges around the lawn. It's kinda cramped and I only ride out there to test out mods to my scooter.