I have a confirmed female (she laid eggs once) midas
hybrid, and even though she's only 75% midas and a
female, she gave my oscar quite a beating when she reached sexual maturity. He was twice her size at the time.
Given that, I would think that two male midas housed together would indeed tear one-another apart. 70 gallons is not a large tank for an adult midas, and when these fish decide they don't like a tankmate, I don't think it would matter
how big the tank is. They chase and chase and chase. The other fish can display submissive signals and flee as much as it likes -- it doesn't matter to a midas.
That said, I kept my midas and oscar in the same tank with a divider between them for a while, and now they happily live in an 80 gallon together... as a mated pair
. They may be incompatible species, but I'm not going to tell
them that
Sooooo.... to answer the original question, yes, you can
sometimes keep them together in a large enough tank if they are a mated pair or two females.