Snotzo - Moving the valves away from each other is an important discussion and more needs to be said. The Commando valve layout is still based on the smaller 650SS bore. With a larger bore you can move the valves, re-angle them and go to bigger diameters. It takes someone like Herb Becker to go all out and weld a solid bar into the Commando guide bores and start all over. Once he's done it, other people can follow. The short stroke engine being built will have 81mm bores so there is room to both move and re-angle the valves. Ports can be welded and moved as well.
JS, there will never be an optimum position of rocker arm to valve, so allowing for this we end up with a compromise.
It is usual to try to obtain a contact path for the valve tip of the rocker arm and the end of the valve stem, such that the path, although curved, will stay as close as possible to the centre line of the valve stem, from valve closed to valve full open. That the valve angle can be moved is common knowledge, but little seems to be understood about the resultant contact path.
The problem here is that the rocker pivot shaft is fixed, and ideally it could do with also being moved, to better compliment both the changed valve angle, and any seriously high lift cams. Those wishing to investigate this should carefully measure up a head, then lay out the rocker and valve using either CAD or a drawing board, preferably larger than life to better see the contact path.
Such a modification might be applicable to your lengthened rocker arm, the longer the arm, the more favorable the arc of the contact path
Some may say why go to all this trouble, valve angles have been changed before and nothing bad has resulted.
Fair enough, but how close has the result been to a disaster as a result of the rocker tip contacting the edge of the valve stem at full lift?
When serious changes have been made for competition at the highest level, it is part of the nature of the top competitor to be always striving for that last ounce of performance, and if a sweeter valve action can be obtained, the whole valve train, indeed the whole engine benefits.
Hopefully so also does the rider.
Posted in the hope of encouraging further discussion.