If your parallel and ctc was correct as you say, and assuming your clutches were also operating properly then you most likely had something changing under load. A couple of relatively cheap OSP and Evo parts would have helped with that. I have worked on quite a few 1100s that the owners say their alignment was good, whether that was them or their dealers were telling them that, and it was not. Not saying you are one of those guys but dealers that are willing to learn what the issues are caused by are having success with the parts that are available.
Not trying to change your opinion on the sled you have, I think you are pretty set on that, but there are people changing belt blowers into sleds people love. I know of 3 people on here that brag about non belt issues, far more lamenting about the problem. This is the norm on any forum.