Coming along huh!
If you want more than 60" lift height you would probably move the tower/upright end of the lift cylinders upwards, but in doing so you lose a bit of lift force. The factory hydraulics have a relief valve in the 3pt assembly which i believe is set at something like 1700psi already. What i mean by that is if you were designing towards a lower pressure but end up not having the lift force you wanted, you can always go up on pressure and until you pass the 3pt relief pressure you're not doing anything Kubota didn't design it to handle. So my personal opinion would be get the lift height you want and then tune pressure to suit your desired lift force and you will likely still end up way below 1700psi anyway.
For reference, here is a B219 with cranked pressure picking up WAY more than 500lbs. Possibly 1000lbs.
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There is a pressure gauge mounted on the tractor in these pics and even picking up MUCH more than at factory pressure, it still stayed under 1400psi for most of this lift, until it got up near the very top at which point it took about 1800psi.
I'm not sharing this to recommend you ever try to pick up 1000lbs to 6ft high with a b7100 (this is a silly anecdotal showoff pic, not something practical or useful) but it just goes to show you that if you have 2" cylinders you're going to run out of rear counterweight to keep the back wheels down, before you run out of 'headroom' to make pressure on the factory hydraulics. If you have 1.5" cylinders then yeah, you probably can't replicate this dumb idea picture on factory hydraulics without taking some risks with your engine driven pump, but can you still lift over 500lbs to full height basically no matter what? Yes. So i would adjust the lift cylinder placement on the uprights to get your desired lift height, and then adjust your loader relief valve to get it to lift whatever you want it to based on your normal/available counterweight.