If by "... reduce the amount of rotation..." you mean "Will the engine sit straighter in the motor mount?" the answer is yes. Think of it this way: if you have the same distance (11.25") from the LE to the "prop" on each side, in theory you'd have 0* of right thrust. The further you twist the engine clockwise (when looking down), the more right thrust you'll get. With 1/16" on each side of the engine in the motor mount, you've got enough wiggle room to adjust the right thrust as Bingo Field suggested above.

This all assumes the the firewall is build with 0* of right thrust. On a lot of kits, the right fuselage side/doubler is shorter than the left side, so there's automatically some right thrust built into the airframe. You might want to check your firewall to make sure it's 90* to the fuselage sides. I looked at the directions for the Tiger 60, and it appears that's the way Goldberg designed the firewall, and all the side thrust comes from mounting the engine "crooked" in the mount. While there's nothing wrong with that, I'd be more prone to mount the engine square to the mount, and shim the back of the mount to develop side thrust. One or two #8 washers would probably be all you need.

By the way, this is one of those deals like love, grenades, or nuclear warfare: close counts. While you don't want any left thrust, even if you build the Tiger with 0* right thrust, about the worst that happens is the plane pulls a little to the left on takeoff and vertical uplines. If you get too much right thrust, then it'll pull to the right. But anything between 1* and 2* will work, especially on a Tiger 60. As you get more and more familiar with the plane, you can experiment to see what works best for you. As Bingo suggested, you can easily put shims or washers between the firewall and the back of the motor mount to adjust side/down thrust to suit your needs.

You should end up loving your Tiger. I had one of the 40 size ARF's, and thoroughly enjoyed flying it. Let us know if you need anything else.