JS
the Sifton 480 was already asymetrical before you started playing with the ramps, your post however does raise a question, just how much valve lift is really necessary for top performance at 9000 rpm with a 750 short stroke Commando at a land speed record attempt ?
Most will be aware that the lift is necessary in order to obtain a reasonable period where the valve is open for maximum flow potential, the most often used yardstick being 25% of the valve seat inner diameter.
The other problem is how to arrange the cam lobes for best results. Norton and BSA are both restricted by having all cams on one shaft, whereas Triumph, Matchless and Enfield have separate camshafts. Tom Sifton made his choice years ago, and most probably his choice would still be considered a good one, but without any means of adjustment, getting it wrong could be a disaster.
Others may have attempted to increase the valve lift beyond .480" in the past, and likely may have been sucessful, but to my knowledge only Tom Sifton's 480 cam has survived to still be considered for top performance events such as that which JS is preparing for