Don't expect to get a correct answer from someone who actually does hydros
Edit: Captain and I posted at the same time. My comment was not directed toward him. My understanding is the same as his, and, as far as I know, neither of us does hydros
Im hurt. I run a hydro shop that caters primarily to the dive shops in my area. We do the plus rating when requested by the customer, and all the shops here in town ask thier customers if they want the plus rating. But no worries duckbill, if you need a hydro let me know, I will sure to do it wrong for you and overcharge you. .