I do Tailwheel training in a SuperCub and I often can't see the instruments, especially if the bloke in front is on the large side. It is not a big deal - you have to trust them to nail the correct speed. You can generally tell if the speed is not stable by the wind noise and attitude changes.
The student has to work the radio and flaps, but the only control that I can't reach that I really worry about is the mixture.