ASRock x79 Extreme4-M dual channel kit dimm seating

[MxMatrix]

Hello community,
I've got some spare and left-over parts and decided to put them together.
- i7 3820
- ASRock x79 Extreme4-M
- Kinston Hyper-X 2x8 gb ddr3 dc kit
- Scythe Big-Shuriken-2B cooler

The cooler hovers over the b1 and c1 dimm slots, making them nearly inaccessible after the cooler is installed.
Now, it's a 4 dimm slot mobo, capable of dual, triple and quad channeling. So a dual channel kit should work.

Poses a small show-stopper, I have to seat the dimm's right first time. Or lose a lot of time and effort in reseating both dimms and cooler while investigating the right composition.
I's like to do it first time right so taking a bit more time asking you for advice.
The manual is extremely vague on this matter and actually only covers a quad channel solution.

Which dimm slots should be populated for a working dual channel setup on this mobo?

Choices are:
a1
b1
-cpu
c1
d1

Please help me out

 

[MxMatrix]

Seems I've found an answer, judging from various sources memory alignment should be closest to the cpu in general. So placed dimms in b1 and c1. It works. EUFI reports dual channel is active.