Hi Gillenvy, I moved to CCR for more gas especially in currents etc.
I breathe deep and hard when working hard and OC is just useless for me. (I can watch the needle moving).
Let me state the caveat up front, I believe there is alot of difference between people for DCS, O2 sensitivity but also their CO2 sensitivity.
YMMV.
Also 45 F is about 7C, colder than I have experienced (yet
)
10 (50F) is my coldest and I have had a few heavy current dives at about 13 (55F).
I have completed more than a few dives where other OC and CCR divers could not get down or were not comfortable to continue. On more than half of these occasions I had to stop and catch my breathe on the bottom.
My rebreather performed flawlessly to my knowledge. It only took upto 10 second or so to bring the breathing under full control and ready to go again.
I don't muck around with extending the limits of the Dolphin scrubber or using a partially used scrubber or sorb. Especially not for deep dives. I change it happily as cheap insurance. I also have a 3mm neoprene cover that goes over my scrubber as well as loop covers.
My advice would be to start with fresh sorb for the cold current dives, and to pre-breath it at least 10 mins. I also think some Sorb work better than others, efficency wise.
Hope that helps. Wiz