1. Normal structure
As some model the distance is big (more than 1.2m), then the gap on the idler side will be little biger than motor side.Then they use double motor.
X brand: they use 2 motors, like 2 person to carry the board.And the most important is their motor is very small, single one can not lift the board!
① special design of bracket to decrease the gap. Similar solution as Range Rover Vogue, even the distance is 1.4M, it work well.
①nobody can assue the 2 motor in same speed. Normaly, the tolerance is -+1RPM, that mean there are 2 rpm difference, total 1.4s, it means: 2/60*1.4/0.38=11% difference (0.38 circle per time). This means 1 motor work 11% more than another.
②installation will be very complicate, because 1 motor faster than another.
③ECU and motor easy to be broken. As 1 motor stop but another still work.
④Power consumer bigger.
So， using double motor is not the way to solve the problem.
The only way is:
1)Decrease the distance;
2)better design of bracket;
3)control the machining tolerance;
These are what Woden already done and work well.