If your fish are eating and healthy you may not experience any loss. Just ramp up slowly over 4 days instead of 2. I've found that most common fish tollerate cupramine very well at the recomended dose. Some of the more delicate fish can be tricky though.
After experiencing some painful losses because I was not careful enough with my QT procedures losing one or 2 fish for long term peace of mind feels acceptable. SPYDR I think you need to find a way to make a QT tank an option. It is inconvenient at best but a neccesary long term investment in the hobby IMHO.
I believe Seachem recommends half strength for rays and sharks. I also would not use Cupramine with established live rock/sand as the Cupramine will kill all living things in the rock/sand and you will have ammonia problem which may kill your fish.