David Weaver
yes (the big mouths are a matter of sloppy plane making or setup and not due to a mechanical need - or on old wooden planes, maybe due to a lot of wear).

In something like an older infill where the inside of the mouth above the sole is carefully filed to match the cap iron, the mouth can be almost nothing and be no detriment to the cap function, but there's no great reason for it to be that tight. Something like a 16th is nice on a smoother.