Cathar, I was thinking about how you said that your cup:jet ratio was such that the "rebounded" water would hit the wall just after rebound. For some reason I got to thinking about parabolas and hyperbolas and focusing the rebounded water to a certain area to acheive added cooling after rebound. Haven't gone any further with that thought because I also wondered, do you know if the rebounded water is rebounding straight back out of the cup or could the rebounded water also be going straight back into the jet and slowing it down? Obviously your block works great and you've spent much time designing it but I haven't seen anyone mention where the exiting water is going exactly. I hope you see where I'm going with this
I was just wondering if exiting the rebounded water to somewhere else besides back out the cup might help the impingement effect some.