Line pressure after shift kit

I installed a basic shift kit during my 904 overhaul. It came with a stiffer regulator spring. The instructions stated to install the spring with the aduster all the way out, and if you wanted firmer shifts to go back and adust it in up to .260.

When I installed the trans and checked line pressure, it was 75psi and 100 psi with the throttle lever all the way back. I had to pull the trans back out before driving it, and I was thinking of increasing the pressure a bit more why it's out. I guess I'm used to more modern transmissions where 100-150 would be the higher limit (but they also have electronic pressure control).

That got me thinking, what is a maximum pressure that one could run before causing issues? I've searched all over the web, but most specifications I can find are just the stock ones listed in the service manual.

Other than the risk of making the shifts too harsh, what are the hazards of cranking up line pressure? Shift timing? 2-3 overlap?

The only mods done during the shift kit install are the stiffer line pressure and converter valve control springs. 3rd apply seperator plate hole was drilled to .140, and 2nd apply to .98. I was supposed to drill out the 2/3 timing port, but on my seperator it was already way larger than the size they suggested. I'm not sure if that makes the 3rd shift take longer or less time.