Wow, nice block Cathar.
My first time here and I'm blown away how in depth everyones gotten with designing water blocks, very cool
I was really taken with the jet or pipe desing you have and it got me thinking.
What if, instead of the pipes being on the top plate they were on the copper base and had an inlet (or exit) channel throught the base to allow the water to flow through the pipes and around them in the reservoir area. Something like a heat pipe. Use the copper "pipes" to take away the heat in the copper base.
My experience welding and fabricating got me thinking of how well running water over a freshly welded pipe cools it down, and running it through it works even faster. Your design just put those two thoughts together.
Anyway, glad I discovered this site and again, nice block.