[Volenti]

well you'll have to use you judgement, without knowing what mounting hardware you're using it's impossible to say what tension is right, think about how much force the clips on the air cooled heatsinks apply to the core and try to emulate that.

Just be really carefull when adjusting not to let the block tip too far one way or another, remember the MTBD (mean time before death) of an XP without the core contacting the block is a second or 2.

if the temps don't seem to change very quickly then the motherboard may only be using the socket thermister, test this by turning the pump off, and letting the water block heat up a bit, 5-10 degrees, then turn the pump back on, the temp should drop very quickly (5-10sec) back to normal running temp.