Modified the A-Struder to better fit my version of the B-Struder ( http://www.thingiverse.com/thing:2243325 ) :)

It's smaller in size, and it secures the motor with a pair of 200mm x 4.8mm Zip-ties.

If you want to add a suspended counter-weight, just tie it to the zip-tie on top of the motor.
Simple and easy.