What or where is the proper location for the tachometer while taking RPM readings? Should it be behind or in front of the prop or does it matter? Thanks!

It works both ways, but behind the prop is a lot safer.

OK thanks! I thought so, but just wanted to be sure.

Two advantages to staying behind the prop is that you won't have to reach over the prop arc to adjust the needle valve, and if the prop was to fly off or break, you are in a safer position. But, you should still wear safety glasses.

David