The normal standoffs won’t fit through the holes in the pibow ‘layers’, the holes are only big enough for an m2.5 bolt. Making the holes big enough would mean several bits of layer would fall off, or at least become very flimsy.
The coupe case in particular would otherwise be a great case to use with HATs. Is there any way to make a standoff that will wotk with a Pi 3 and a coupe case? If not, it looks like the only option is some robust tape over the hdmi and audio sockets to prevent bits of the hat shorting out.
A little bit of Duck tape on the underside of the HAT/pHAT, which should be fairly unobtrusive.
Some creative modification of the Pibow, drilling larger holes.
Some long screws, inserted from below, and then some bolts as spacers.
Having said that, I’ve never had any trouble with shorting against the Pi. We try to design our HATs and pHATs so that there aren’t any solder points in those areas, and we use HATs and pHATs with Coupé cases all the time with little to no trouble at all.