Foxton probably is 600-700 cfs
The gauge at Bailey is probably 20 miles upstream from Foxton and the Grant gauge is 10 miles above that. They are probably correct, and there is probably also 700-900 cfs in the Foxton run. We ran it Monday and I was estimating it was 600-700. The difference between Bailey and Foxton is all of the creeks and side streams coming in. There were culverts dumping probably 50 cfs at a time into Foxton. I would guess that Deer Creek and Buffalo Creek are dumping lots of water into the North Fork. We talked to a boater that lives along Foxton and he uses Waterton gauge - Trumbull gauge (which is just downstream of Deckers) to estimate the Foxton flow this time of year.
Anyway, Foxton was fun; lots of good surf waves. Waterton was 2400 cfs and also definitely worth running and hiking your boat; a big water feel that we don't get very often along the front range.