So you and Keith are BFFs now? He's a very smart guy!!! You may find it easier to mount your beam before mounting your wheels. I kept coming across that when researching mine. Looks like you're coming right along. Question - with your mega awesome building that I would go crazy inside of (building envy), couldn't you suspend an I-beam down the center length of the roof truss for a trolley and hoist? Or would the truss not support the additional load? Just thinking out loud. You've probably already considered it.