I would get the Horizon Tach/Volt Meter and use it to learn with, they do come in handy and it's good to have one in your box, my TNC is always with me. If I didn't have a Tach when I was doing the tune on my gasser I could have set up up way out of it's best RPM range. That's a torque thing. I wanted to get my engine around 7000 to 7500 RPM. The first prop I had was too small and it was hitting 8700, Zenoah states 9000 max but the best torque between 7 and 75. I changed props and it's right at 7300. I couldn't tell with this engine what it was putting out, I'm not used to hearing it yet. I needed the Tach. I will use it on this engine for quite a while when I change prop size or even prop make. For small two stroke glow engines I have been doing them so many years i just bring them up to full rpm then back off until i hear the drop, I may even do a pinch test if I can get to the main fuel line? Most the time I'm pretty close. When I was a pit man for racing class planes I always used the Tach. Racing is different, too lean and the engine craps out, too fat and the engine isn't running at peak. Buy a Tach!! You will use it and learn a lot.