Many riders with the desmo head on their PT have come across the need for thicker closing shims. With my 500 head without shims I needed to start from scratch. Having some shims left over from belt drive desmo heads, the valves only needed to have a new groove in the stems roughly 4~5 mm lower than the original to have them instead.
As the 500 head needed new valve seats, larger 600SS/Monster valves were taken and those modified with new grooves, and now desmo adjustment can be done with standard available shims from your local Ducati dealer. Problem solved!