Do you mean getting on a plane or staying on a plane once there?
For getting on a plane the straps position doesn't really matter as you won't use them while you are pumping the sail with your arms and kicking the board forward with your legs. Anyway to get on a plane and stay there in marginal winds you need a quite big fin on your board and to be able to control the big fin you need your straps in the outboard position.
Anyway on some boards not really made for light wind planing i.e. waveboards, there's no such thing as a big fin and outboard straps. Here you will have to be very lightfooted when you pump (else the fin will loose grip and you will spin out). On the plane you can successfully use a little forward and upright position (and again be very light on your feet)