Been there before. I have converted sevreral helicopters to CCPM. It is not as hard as it looks. The metal side frames on a shuttle will make it too heavy for a 28, Yes i made some for a Shuttle before.I would use G10 and plastic stanoffs. From your print I think you need to move the rear servo forward.

Hirobo does sell a CCPM Shuttlh just get the manule and coppy or alter the design .You could keep the same servo tray and use bell cranks . Sounds like a good winter project!
Michael