My temps at full load (using a computational quantum mechanics or the HPL benchmarking software) were 58 - 65 C.
I first tried lapping the heatsink as it had a noticeable bow and a fairly rough surface. That plus Arctic Silver 5 did not change the load temps.
I bought a replacement heatsink, which has 25 mm fins instead of 12 mm fins. Again, no noticeable improvement.
Then I bought a 60-to-80-mm fan adapter (and made a custom adapter plate to attach to the heatsink shroud) and tried larger fans having decent static pressure capabilities. The Sunon 80 mm (
Sunon 80mm Fan - 3-pin (KD1208PTB2) - FrozenCPU.com) was the only one providing a noticeable improvement - load temps 55 - 60 C.
My latest effort was to have custom 70 mm x 70 mm x 40 mm heatsinks made (I bought 10 b/c it was the same price as buying 2 and I knew I would need at least 3). Paired with the Sunon fan the load temps dropped by 8 - 12 C. With the computational quantum mechanics calculations the load temps with all 8 cores at max are now 45 - 52 C.
My next step is to make custom fan adapter shrouds to better attach the fan to the heatsink.