My feet are normal sort of width, usually 41, and I've never had a problem with my instep.  With this clog I found that the 41 was very tight over the instep (didn't try the wide because I read that it's v wide in the heel...I just wanted it deeper, not wider).  Tried a 42 and it's just huge, way too loose all over, and seems different from the 41s because the top of the shoe extends back further, more like the open-backed one I have and get on pretty well with in 41.

I've given up, and I'm exploring clogs in other brands..