This is exactly where you are making poor judgment. In this application of barrel retention on an open top Colt, Samuel had it correct.
Arbor, barrel, and barrel location foot against frame must make solid contact. All at the same time. For the wedge to hold properly it only needs pressure applying front and back. Defiantly not top to bottom which is counterproductive to the holding power of the wedge. If you feel you need to fit the wedge tight top to bottom to get it to hold, you are actually robbing the holding power of wedge from front to back which is the proper force. Your statement of " Snug wedge thickness fit in both barrel and arbor slots helps the lower lug pins support radial torque pressure as well as providing a friction load against backing out." Are you trying to kid me, do you have any idea of the shear strength of those 2 locating pins that are off center line of the bore? Please. Proper metal to metal contact/fitting and with a wedge that builds pressure and actually compresses the parts together with proper friction is all that is required.