I think you need to increase the powertune a bit. This is my config:
With this I am getting about 3.2 MH per card.

This is a very interesting project.
It inspired me to also investigate in this area too.
So I have bought the cluster version of the your boards which is available now: Odroid-MC1

I already bought one case from you, and am very happy with it.
Do you have any more on stock currently?

The XFX are sold now. Price update for the MSI !

Another price update !

I am selling some GPUs here:
https://bitcointalk.org/index.php?topic=2504025.msg25608939

1 GPU sold. Update first post.

Yes, escrow is ok. Updated post.

Because I changed my mining setup to NVIDIA cards I am selling the following items:

3 x XFX Radeon RX 470 RS Black Edition 4GB ... € 210 each - all sold !
https://preview.ibb.co/jxjACw/20171201_172029_bitcointalk.jpg

1 x MSI Radeon RX 470 Gaming X 4GB ............ € 220 reserved
https://preview.ibb.co/gsKMKb/20171201_171009_bitcointalk.jpg

2 x MSI Z170-A Pro Mainboard ....................... € 90 each
https://preview.ibb.co/c2gOXw/20171201_172810_bitcointalk.jpg

All GPUs and MBs are in their original packaging.
All GPUs have Hynix Memory (H5GC4H24AJR) and are easily hashing 28.5 MH/s ethash with custom BIOS already flashed.
The mainboards have only been running for some days to test, but are working fine (with up to 4 Cards).

Shipping inside EU with buyer paying costs. Escrow is ok if buyer pays the fees.

I have a couple of these https://www.inter-tech.de/products/ipc/server-cases/4u-4129-n
You can remove all the drive gages and the fans in the middle and have enough room for 6-7 GPUs.

And they are available in Europe (Germany).