I found that anything over a 65" wingspan is easy to see, even for a low wing which is what you want for a trainer. I do have a problem with using a Cub for a trainer however. The Cubs can be a little unpredicatable when landing. A touch too slow and and it'll tip and go down. Cubs don't like to fly fast or do aerobatics which means that you couldn't pass our basic wings test with a Cub. Steering on the runway on most Cubs is also a challenge as it ground loops easily. A sig LT40 is a better choice with a 70" wingspan but you I don't know if you want to boither getting a nother plane now.