Yup tried that as well and it does work, however it is gaining access that takes the time - seat, then rad shrouds (Assuming the bolts don't spin on the nasty captive nuts in the plastic guides) then tank, then hope you can get your hands in to the front rocker covers - I used to drop the rad vents off and move the rad forward but mostly because I was doing other work like replacing rad mounts and hell, do the plug at the same time with a ground down plug socket and long extension, then reverse procedure..........
The actual valve clearances are a 10 minute job it is just the rest that takes the time.
I used to be able to do valve clearances in 30 mins from start (ie complete bike) to finish (bike ready to race)
Snap-on used to sell individual feeler gauges as replacements for their full sets, bought the right one and bent it to the required shape.
Mark