Not at all is the correct way. Increases cylinder temperatures in the top of the cylinders, limits coolant flow overall which out weighs any gains from it. However, if you're insistent on installing it, having a machine shop inserting it correctly/evenly, boring the cylinders to account for any inconsistent pressure on the cylinders applied by the block guard and then finally decking to ensure a true flat deck surface is maintained after installation. So, as aforementioned in this paragraph, the correct way is not to install one at all. 81mm bore will take a very nice amount of CFM as well as produce a nice amount of power on healthy stock sleeves with a PROPER tuning.

Enjoy.