[EricH]

Originally Posted by InFlight

Two stage 10:1 gearbox with Vex gears is no issue....

With a 12 tooth CIM gear.

Just as a point of clarity, VEX could commonly refer to any one of the following:
-VEX Robotics (division of IFI)
-VEX Robotics Competition (VRC) (robot competition using VEX EDR and IQ robots)
-VEX IQ (robot parts series designed for the same market as LEGO Mindstorms/FLL)
-VEX EDR (robot parts series designed for the same target age as FTC--the original FTC kit...)
-VEXPro (robot parts series designed for FRC)

From the context, you're referring to VEXPro, while the OP is referring to one of the other items on the list, likely VRC or VEX EDR (or both, given that VEX EDR is used in VRC). CIMs don't work very well with the EDR line.