For what it's worth you may want to check out this article, maybe you already have this info.
Method for Turbocharging Single Cylinder Four Stroke Engines
I've read that article a while back which caused me to go to into research mode to see if I should even mess with turbocharging. Here is what I found and what the article doesn't tell you is that what it says is true and makes sense...for a carbureted single cylinder engine. That is what all the research that when into the design of the air capacitor dealt with. Single cylinder, carbureted engines where the carburetor causes complication with air fuel mix irregularities that will happen when trying to force air from a turbo through the carb.
In fact, every bit of info I found dealing with problems faced with a turbo on a single cylinder engine was with carbureted engines like you would have with go carts and the like. With the P5 being fuel injected and being able to adjust the air/fuel mixed based on real time figures from the machines sensors with a programer like the DynoJet Powercommander v with auto tune, which is what I'll be running, those problems don't apply.
Case in Point, you can buy a bolt on turbo kit for both the Yamaha Rhino 660 and 700 that is basically an identical system. The 660 being carbureted, see's very little gain from the turbo while the 700, which is fuel inject, see's a good bump in performance. This has me hopeful that the P5 will do well with a turbo but this is unexplored territory for the little guy so we'll just have to wait and see what I can do. I am by no means an expert on turbo's though so it will be a learning experience to say the least...lol