this is one of those "i haven't seen your feet" moments
i wear a 7-7.5 shoe in everything (cleats/dress shoes/trainers/hiking boots etc) in cleats i can wear adidas or GAIA(hey i play ultimate what can i say) i cannot wear NIKE(to much volume except for maybe speed TDs)
in the old days i wore a sz 7 flexon comp(293mm boot sole) when i worked for rossi i wore a sz 7 course kx (294mm boot sole)
now i work for LANGE and for my everyday(ski and possibly stand on the side of a course or under a tent in Canadian winter seriously -30*C some day) boot i am in a Comp 120 LF sz 7(299mm boot sole) with a foam liner.
My foot is relatively low volume, medium arch, high instep, very narrow heel/ankle up to a semi sprinters calf(hey i play ultimate).
what i know about plugs is any thing can be made to fit(i have done it)...i personally can wear the sz 6(282mmish BS ZB/ZB flex) when it is shell fit my foot touches everywhere there is a bump when the liner is in i'm good for about 4 runs of GSey turns if it isn't really cold(this in a boot that hasn't been punched or ground...)
in the sz 7 (298mmish BS ZB/ZB flex) plug i can wear the boot til noon again if it isn't really cold (again no punching/grinding)
with my own boots all day skiing or standing not an issue
you said "060, (291) would be very snug or the 070 would be a little spacious"
i never used spacious when refering to anybodies plug boot, ever...