I have a Tower Hobbies Digital Mini tach and I guess it works alright. Seems though I can't get a steady reading on it. I have a Saito 72 so maybe it's the engine, but say for instance, at idle it will show between 2,200 to 2,600 or higher rpm and it really jumps around. Same on the high end. And when I angle it up or down a little the reading is totally different. Is this just how these tachs are or am I doing something worng. I hold it behind the prop about 3 or 4 inches.