I would use a second PI , i couldn't get my A6 or A7 to work to gather because of the cable form the miner to the AUC @ the miner end on the 741 the plug is bigger then the one for the A6 miner end if you can make a plug to either the A7 or A6 miner end form either miner that might work or try a USB HUB then plug that it into one PI with Custom software like Minera that might work . or edit one of the Avalon images to work with both a A6 and A7 and use a USB HUB that way but i that may not work well because of Avalon's software but should with minera or the black screen for CGminer running UBUNTU 16 .


I run my A6 and A 7 with Minera https://getminera.com/ but not on the same controller i use two PI's that are not RPI  and compile Ccminer 4.10 to run with both on two controllers , and haven't tired with a USB Powered HUB On the same controller .