I don't think I can expect more from them with 4-4-4-15.
I tried 1040Mhz up to 1.98V (bios) but it wasn't stable at all.

Regarding temps :

I placed a small temp probe between the HS and the chip (as far as possible) and I measured around 32°C idle and 37°C load, with 1.80V.
This is with one stick, placed in DIMM 3 (second row, first slot).

The one closed to the socket (DIMM 1) (first row, first slot) and near the NB gets very hot, measuring temps of 51°C.
This was due to the heat coming off the NB (extremely hot), which of course dissipates his heat to the HS and memory in general.
Having a small fan blowing at the NB helps.