Hi Woodnerd and welcome to the FOG [welcome]
Festool Countersinks with depth stop are combined with a pilot bit, the "zero flute" as you call it would probably not work with a pilot bit added due to its intrinsic desgn.
Have you tried a Festool depth stop countersink bit such as Brice Burrell posted a picture of, in reply to your post on TalkFestool?
I think you would be pleasantly surprised at how good they are. [smile]
I posted a review on countersinks on here a short while ago you may be interested in it and the subsequent comments.
Regards Rob.
http://festoolownersgroup.com/festool-tool-reviews/short-review-of-countersinks/