Not to be the one to throw in the towel, but have you thought about just getting a MU10/100 ?
Haha every single day, I just don't have the capital! I have a general plan laid out to upgrade this cell for a while and hopefully within 12 months swap everything out for a 6600 with a pre-installed 7th.
There's so much other stuff we still need in the company, with the robot just baaarely squeaking out the parts, it's hard to stop everything else and just get it done like real adults!