My original garage door was made of some type of composite board, 16x7. At least 3 coats of paint on it and it still absorbed water, my garage door opener kept breaking gears, Craftsman and they were plastic, but plastic wasn't the problem, that door seemed to double in weight during rainy periods. Went to a steel door 15? or so years ago and no problems, my 30 year old garage door opener hasn't had a problem since the door change.
My barn has an 18x8 steel door with a Genie garage door opener, not sure where that Craftsman brand is heading with the turmoil at Sears, but I would probably avoid it now. My Genie door opener is about 18 years old? No issues opening a bigger door.