Hi Neil,
From your figures it looks like your vO2 is 1.22 l/min. At 1.22 you could run 45% through the 60% jet for a loop of 30%. 50% through the same jet would get you a 37% loop.
This is of course if you could guarentee that your vO2 never changes!
If you were to do a dive to 30m looking for an ideal pO2 of 1.2, and assuming that you had a high and low vO2 of 1.6 and 1.1 45% on the tank should do you nicely [although you still need a pO2 gauge]. At the high workload you would get a loop of just over 21%.
Do you have my spreadsheets and tables for Dolphin gas and jet matching? If not send me an email [not a PM] and I'll send them to you.
My vO2 is generally in the 0.8-0.9 region, with a working peak of 1.2. I tend to take at least five readings of pO2 vs depth every dive,and periodically do an exercise check to verify the figures. I dive the Dolphin conservatively and a hyperoxic rather than hypoxic loop is normally my problem.
For the same dive as quoted above I would be able to use 40% through the 60% jet.
Have a look at
Semi Closed Rebreather diving gas calculations. if you haven't already, this runs through the formulae for the gas matching, and if you have any further questions just ask!