Hi Cub,

Replying by the number:

1) I never saw a Tach That was "off" . That covers the original Heath Kit Thumb Tach (before your time) right down to the H9 Micro which I now use. It gives the same readings as the larger variety. Matching the engine /prop. set up will be done through in flight experience.

2)Airborne you'll gain about 1000 rpm + or - . DO NOT try to compensate with your ground settings which should be at max for each prop size.

3)Can't help you with on-board Tachs. But you better get one that shouts the numbers out as you can't take your eyes off your plane.

Repeat after me KEEP YOUR EYES ON YOUR PLANE !!!

Hope this helps.