I would not be so concerned with the resistance of AL : CU.
If it is big enough (for me) to work with, and get screws in it to hold the big wire(s) securely, seems like the resistance would still be less than the wire.
Something about the AL discussion I think is very important:
bus is tin-finished aluminum per UL 67
I am not so big on 'owl s#!+'.
I would rather not have any issue, than smear goop on it to hopefully stop a known issue.
Fine for the combiner but I don't think it'll take a high-amp hit from an inverter if a couple motors start up at the same time.
Don't most of those big inverters have 2 or more input wires per +/-?
I had a big 24V Trace with 3 + and 3 - inputs... I think.
Why not run them straight to the battery terminals?
There would be 10 reasons that is a good idea. There could be 10 reasons its a bad idea.