But by this logic you are saying that services such as Rinkya
and Sato (who do not deal exclusive with cels) are less likely
to store cels properly than other services, which obviously
isn't true (and superior..).
Anyway, though I can't
vouch for this service personally, other parties who I know
personally as reputable have used him reliably for cels, and I
would assume he knows how to handle them besides rolling them
up in tubes or folding in a box. If one is terribly concerned,
you can always ask him directly.