If this would be any help...
block size is 50 x 50 x 10 mm, its hard to find thicker copper block here in Croatia (still searching ...)
The thickness of the block allowed me to drill it with 6 - 6.5 mm bit only, so the block is ( I think) flow restrictive and it has too many sharp turns, but it performes good enough for me (all I wanted is quieter PC, and after glacial 2400 hs/fan, almost anything would be quieter...
The rig is AthlonXP 1800+ @ 1666 MHz (11.5 x 145), Task millenium midi tower, Micro jet 1000 pump, heater core from Lancia prisma, Sunon 120 mm @ 7V ... 32 C idle, 37 full load... and quiet enough...
just looking for quieter fan...but can't find anything else but Sunon here...
Big & Jay... thanx