Im sure the 30 day ext will be no problem. HOWEVER, since the change to 60 days visa exempt immigration are MUCH harder on individual border bouncers (go with a visa bus seems ok). Basically i had the same issue and they made it clear that the 60 days is 60 days (or 90 days) then leave leave not just for a short period. Those need a proper visa and it wont be long before entries start getting denied