As a gunsmith/accurizer, I'm impressed with the design of the 66 for an iron-sighted accurate plinker with longevity, but regardless of how inherently accurate the action/barrel design may be, the rifle's actual performance as a scoped, tack driver is limited, due to the sheet metal receiver cover IMHO. A barrel-mounted cantilever scope mount might improve accuracy, but would probably not be right for the rifle today, considering collector's value and aesthetics.
We all have opinions, and I previously stated mine about MY particular improved Shilen-barreled, 10-22 Deluxe being, not the ones coming out of the factory today. Your results may be entirely different and I respect your opinions.
FYI: My particular 10-22's accuracy is documented on the "Prove-It" website, with a photo of my target's, 10 consecutive 5-shot groups at 50 yards averaging .37". That's not common for a factory 10-22, not even for many custom ones. Although it's had considerable tweaking, the only non-factory parts, except for bedding and trigger stop, was the Shilen barrel.
The best part of this particular 10-22 is the added weight of the heavy barrel that improved my offhand shooting accuracy. The original barrel, IMO, was too light for steady holding, as are most lighter rifles, including my CZ455.
(The 10-22 accurizing procedures used on my rifle are documented on Rimfirecentral.com Tips and Tricks Forum.)