This to me sounds like exactly why Steve at Commercial Powertrain wants to install test/tune his own stuff before he hands it over. That to me is worth the extra time and maybe $ upfront. No one here has posted a hiccup or negative thing about his trans or work.
I hadn't heard of Steve or Commercial Powertrain until I read this thread, but my point--aimed at the OP--is that these aftermarket "built" transmissions are very, very complicated pieces of machinery and are not a plug-and-play modification. I have been spoiled working on my Cummins; a lot of mods that make a big performance change are relatively easy to install and require ZERO development on the part of the consumer.
68RFE's are complex, and you will hear a dozen different opinions about the best way to make one hold together under extra power if you talk to a dozen different trans guys or speed parts shops. If you're coming into it based on a little forum research, it sounds as though installing a built trans is as simple as a new turbo or head studs, but getting it to work right is serious business. I believe this is why so many guys with heavily modified trucks are running older, simpler, 4-speed autos or converting to manuals.