Shoulder sitting and wing clipping are two subjects that act like a fence. You are on one side or the other.
All my fids, 2 Cockatiels, A Congo African Grey, and a Blue afronted Amazon are all full flighted and shouldes sitters and I would not have it any other way.
We do have rules and we have a respect for each other when it comes to shoulder sitting.
Shoulder sitting is something that is between you and your fid and you both have to respect each other.
When I got my amazon I never thought she would be a shoulder bird because of her past, but our bond changed all that.