if my memory is not playing tricks on me,
David Vizard did a set of tests once
where he also doubted that clearances as tight as
0.026 inches were absolutely necessary
and he found something like
anything tighter than 0.060
worked equally good for him

never the less
the original article calls for 0.0065 times the bore diameter

certainly the majority of 1994+ Magnum 360s are much looser clearance than that, even though the piston crown clearly is meant to take advantage of squish.

another 'practical ' consideration is
"If there is clearance, how much of that clearance will be closed up with carbon film deposits in a short amount of running time ? "