The clearance between the valves and pistons depends on a lot of things. Some of the info you have stated is correct, but a variable you have not taken in to account is the piston height in the block, or deck height, and the head height.
When we did the machine work on deviates engine, everything was fully blueprinted. The deck height was set to 0, and the squish of the head was .040" and then the head was decked to get as close to possible to 11.5 compression we could. All of this brings the valves closer to the piston when everything is setup and the cams are dialled properly. When the cams were installed, they were less that .5 a degree out from the blueprint spec, so we left them as is.
If any of the steps are skipped or shortcut, there is only one outcome that will eventually happen. Mass destruction.
Your choice, but I know what I would do and what I wouldnt do.......