Re: SBP Shift Kit and Shimano Grip Shifters
The shifter will work just fine on the left side of the handlebars. It has the effect of reversing the direction. When the rear shifter is on the right when you twist toward you it moves to a lower gear and when you twist away from you it goes to a higher gear. When you move it to the left side this changes, twist toward you to get a higher gear and away from you to get to a lower gear.
I've never done a 2-stroke shift kit but I do currently have and use a 4-stroke version. If both left and right side chain are getting loose at the same time then the mount is twisting. If just the right side chain that is getting loose its either the chain streching or the mount is slipping down the seat tube. If you are using the height adjuster that comes with the kit its almost impossible for the mount to slip down the seat tube.
I don't this from first hand experience, but I've heard/read that a right side chain tensioner is problematic with the 2-stroke Shift Kit due the the pedal start? You might contact Jim at SBP to get his thoughts on adding a chain tensioner?