That is an ingenious solution

I ended up reseating the original HS + heatpipe and putting a small fan on the top of the NB. Seems ok, but would really like to get that HR-05 on. The annoying thing is that the installation instructions show an illustration of a retaining clip that would work (2 hooks on each end oriented perpendicular to each other) but this is not the retaining clip that was supplied.

I've recently changed my case (from CoolerMaster Stacker STC-T01 to Silverstone TJ-07), and the ventilation on this new case isn't as good. I've been working on improving both the air circulation and cooling (additional 120mm front intake fan, HR-05 on SB, replaced Scythe infinity with Thermalright Ultra120 Exteme, Scythe Kamakaze 120mm on HS, trying various case fans - SilenX/Scythe/Thermaltake). I had to drop my OC to 3.2GHz as I was getting some instability (and some video corruption during POST).

System appears more stable now with the latest modifications, and I will try and put it back to 3.4GHz tomorrow. I did try vMCH at 1.65, but with no noticeable difference in stability.

Current voltages are:
vCore: 1.3750v
vMCH: 1.55v
vFSB: 1.40v
vICH: 1.20v
vDIMM: 2.2v

Temps (if I can rely on the readings):
tCase (cpu): 27C idle / 49C load [SpeedFan readings without offsets]
tJunction (core): 30C idle / 53 load [TAT readings]

Ambient is 22C atm. As summer is coming, I can expect ambient to rise by as much as 10C (then the fun will start).

I realise that the temp difference between tCase and tJunction is not within specifications (should be ~15C difference so I've been told), but as I have no single temp reading that I can definitely prove is accurate, I am unable to establish the offsets I need to apply. BIOS temp is the same as tCase at idle.

Load program was TAT.

If anyone has any comments or recommendations on voltages or whatever, please let me know.