Have you done away with the slots?, I'm using eight 'holes'(non~symetrical) in my design, venting into a chamber rather than a large tube(pipe
). did you work out the outer tube size so you'll have the optimum area inside?(outside of the 1/2 inlet tube) so it equals the 1/2 tube inner?.
You'll want the res as close to the block as possible as well yes?, to minamalise time spent hot next to cold?. though I agree it's a small temp change only there for a very short time...
With the res, you're going to empty the block outlet into the res' but carry the block inlet tube straight through it to the pumps outlet?. that's the picture I've got. it should revolutionise multi outlet blocks!.