When I learned to fly using rubberbands was the standard method of wing attachment for most trainers and sport planes. I was taught to use 10 rubberbands minimum, and if a plane is over 5 pounds add an additional 2 rubberbands for each pound after that. For example, a 20 ounce1/2A or 3 pound plane would use 10 rubberbands, a 5-1/2 pound plane would use 12 rubberbands, and a 7-1/2 pound plane would use 16 rubberbands. I’ve never had a wing part company from the fuselage, nor have I seen one using that formula (with the exception of bad rubberbands that where breaking to the point there where only about 6 holding the wing on, and those quick let go under minimal strain).

I have 2 students flying Avistars and I have them use 12 rubberbands.

Hogflyer