Think I know the answer, but anyone tried this? Would mean the bung would have to be an inch or two below the steerer.

Obviously if the bung goes too far down the steerer starts to taper out, but if not, is it a problem?

the bung is designed to prevent the steerer cracking under stem tightening isn’t it?
Moving it below the stem as far as the EDC needs would presumably defeat the purpose?

That was my thought, yes. Although the EDC would give some degree of similar support

I don’t think the EDC would give it any real support. The carrier is light and flimsy

I’m not convinced it would fit in the first place, carbon steerers tend to be thicker than aluminium ones, meaning the hole is likely to be smaller.

Don’t Granite Designs do a version of their Stash tool specifically for Carbon steerers/forks.