Sounds like a good choice of servos, I've used DMM servos on a couple of builds an have been happy with them.
You can find the specs of the 728's here https://www.cnczone.com/forums/servo...tml#post183844 Al_The_Man has uploaded a PDF there.
The DMM 1.3KW servos have about twice the rated torque of the 728's so no problem there. It's easy to turn the torque down on a servo, but pretty hard to get more torque out of an underpowered servo. Go Big or Go Home
You may need a brake on the Z axis to keep it from dropping when not powered.
I'll be interested on your progress on this build.