SLING - SingLe INtent Grinder.

Q. What style of motor should I use?
A. 56 frame with base.  If you use anything else, you will have to fabricate additional support.  The SLING grinder kit is designed with this motor style in mind.

Q. Is it rigid?
A.  Yes, it is still nice and rigid.  It isn't quite as rigid as the GIB, so if you are one of those grinders that can grinder 1/2" down to 1/16" by pushing hard enough to move a semi, this probably isn't the kit for you.  Go with a GIB 2.0.