You probably could put extensions on your machine, and you are right, they would probably put too much stress on the drive train, but we put the extensions for an '80 on our 1440. (normal bin) Just weigh the pro's and con's I guess.
We had a Mauer extension on an '85 1460. We got along great with it. I would look for stress areas that may already exist and correct them before installing. The extension is a great tool for opening up fields and when the catch wagon is late getting back. As far as filling time after time, I would be hesitant. It would hold up to 270+ bushel of corn, so we only used the full hopper when we thought it was necessary. Check stress areas daily before minor cracks become major breakdowns. We never did have any cracks in 2 yrs. but it was still something I was always checking.