Multiple encoder outputs into 7i76E

I'm planning a plasma project and could use a sanity check on my plans. With the flexibility offered by Mesa there must be six different ways to accomplish the same thing. I may have missed some of the better options.

I have a 7i76E and some new condition old stock brushed servos and early generation G320 Gecko drives (circa 2004). The G320 gets encoder feedback from the motors but does not pass that back to the control. I want to get encoder signals back to the control. Four servos will be used.

I see MESA offers the ENCY encoder Y adapters. After the ENCY splits the encoder output what is a sane way to get that signal fed into the 7i76E? Here is what I came up with. Feel free to correct anything I have misunderstood or suggest other options.

Option 1
ENCY splitter feeds encoder signal to 7i85 which feeds signal to 7i76E via RS-422

Option 2
ENCY splitter feeds encoder signal to 7i85 which feeds signal to 7i76E via 25 pin connectors

Option 3
Something better?

My ignorance may lead me to easily misinterpret your reply.

Does your config tool let 7i85 firmware run on the 7i76e board and act like a 7i76e/7i85 combination board? Or is the config tool just a convenient way to get both boards working together?