You have asked a basic question for which the answer is more layered than the replies so far. That is, we cannot assume that a crossdraw will be canted reverse of a side draw. The basic spring crossdraw, for example, has long been a vertical; as a shoulder holster but mounted to the belt instead.

So: the verticals are meant to be carried at 9:00 on a righty. The tilted ones, such as the Rosen shown in another post, are meant to be carried at 10:00 and so lay the grip flat across the belly. Either way will keep the muzzle pointed relatively safely.

Your method, of carrying the FBI tilt as a crossdraw: understandably attractive because it conceals well. If you're then still able to cope with the somewhat unnatural twist to your wrist as you grasp and then draw, who then are we to say 'no'?

The only reason you might have to use a so-called 'custom' maker would be if the established makers don't have a fitment for that pistol. And I say that as a so-called custom maker myself :-). P'raps "niche maker" would be more appropriate for what we do?

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Red Nichols The Holstorian