Dont use the v rails.
Use linear guides ... and bigger is better. Suggest 20-25 mm size import rails for commercial use.

Otherwise, pretty much as mechmates were built.

2.
Use ac brushless step/dir servos of 400W or so.

3.
Use a rigid under-carriage, and use only one motor for the long side.
Drive from center.
Vs using sw slaving of 2 motors.
3. is debatable in many ways.

4.
Donīt worry about mass.