I've found that with a 8 pitch prop 1800 rpm is good for landing. I have a MT50 that can idle at 1100rpm, but there's no reason to do that, 1800 rpm is 0 thrust at landing speed.

You can calibrate you electronic tack by pointing it at a light bulb 3600 rpm in the USA with 60Hz, 3000 rpm if you have 50Hz.