I have two Neptune and its instable...
I tried different combination but it's complicated.

Single Asic totally crash after 15min :

http://www.image-heberg.fr/files/14042894688281.png
http://pastebin.com/hvDg9Hkc

5 Asic, 5 x 450Watts connected to a UPS (5000KVA, double conversion online).
Two brutally slow down with many errors (exemple : KnC: 5.1.100 disabled for 300 seconds due to repeated hardware errors)
http://www.image-heberg.fr/files/14042894686910.png

Good for 2 Asic but last, Asic 6 slight decrease
http://www.image-heberg.fr/files/14042894686893.png


Other test with 3 ASIC :

Boot : http://www.image-heberg.fr/files/14042894688980.png (ok)
5 min : http://www.image-heberg.fr/files/14042894689633.png (decrease)
15 min : http://www.image-heberg.fr/files/14042894689784.png (more errors than results)

Actually i try with 5 ASIC, 5 x 450Watts, no UPS, in another room.
At 475Mhz, Asic 2 and 3 crash : http://www.image-heberg.fr/files/14042894686910.png
I reboot Asic 2 and 3, cgminer crash and auto-restart and i set at 500Mhz, for the moment, its stable.
 (5s):3.356T (1m):3.300T (5m):3.285T (15m):2.944T (avg):3.107Th/s
 A:1618944  R:0  HW:5399  WU:43465.0/m

Between delay and instabilities, it is a BIG disappointment for the moment...