Heres a question for you. What if you are Cert in CCR Trimix, but not OC Trimix, then should a shop fill your big tanks? After all CCR only needs those small tanks, right.
Or is the CCR Trimix card the end all of cert cards? So why would a shop not fill small tanks on a OC Cert but would fill big tanks on a CCR cert.
Or what if I want to fill doubles with mix, but only have a CCR Card. What if I want to do a dive that requires lots of bailout gas, in big tanks, should I have to get an OC cert card?