Give us some more info on system like motor wiring parallel or serial, voltage, micro stepping etc drives are running at to get better idea of system.

But still your going to want a ratio applying as 20t pulley direct drive means 63mm pitch which is way too high really and torque low so any stiction will have an affect which is why your bogging down. (2m/min shouldn't be a problem in plywood)
If you use 3:1 ratio you'll triple the torque and put the motors in an rpm range there more happy running and still get decent rapid speeds, well in excess of 10M/min.