mm on startup?

I have used Imperial ACME rod for my machine and used inches to set up in motor turning. How can I get mach3 to default to mm on the DROs when starting up rather than typing G21?

Also for squaring slaved motors x and a, is it standard practice to use the Homing offsets?

Just set up the machine in mm. You can use two different configurations, one for inches and one for mm's.

Or, try putting G21 in the initialization string in Config>General Config

Thanks Gerry. Put it in string.