rocker not centered on valve

[Bevel bob]

The shim caps could have been added to adjust the rocker action across the valve (effectively making the valve longer) ,to compensate for a short valve or recessed seats. Don't see it as a problem. With regard to centering the rocker on the valve I think it more important to get the cam lobe and rocker pad to meet well. A slightly off center contact between rocker and valve is likely to cause the valve to rotate a little. No bad thing?.

[double diamond]

The valve cap and solid rocker arrangement is employed with scrambler models and Diana Mark III, Mark 3 and Mach 1 as well as widecase models (desmo and spring). The set screw adjusters are found in the Monza, Sebring and GT as well as 175/200 engines. If your engine has a hotter cam than the GT (GT’s had even milder cams than the Monza), whomever installed the cam may have (correctly) been concerned with the limited travel of the adjuster/valve tip contact with the stock GT cam. A higher lift cam might run the adjuster off the tip of the valve. Using a valve cap would improve the situation. With a modest lift cam I expect this arrangement will work fine. If the contact point of the adjuster moves out to the edge of the valve cap at peak lift (as it would with a high lift cam) you would have a problem. Since it’s been apparently running this way reliably, you should be ok leaving it as is.

Matt

[Jordan]

A slightly off center contact between rocker and valve is likely to cause the valve to rotate a little. No bad thing?.

It would be a good thing, but I don't think it would be likely to rotate because of friction between the valve, collets, and springs.
Valves that rotate have special arrangements that permit this, involving the collet details I think.
Valve caps could rotate though.