Padowan

If I was you I'd do it on OC, as I know how long you've had your unit. I did my first trimix dive (Duke of Buccleugh - 58m) on my unit after I had about 30 hours at depths up to 55m in warm water and 50m in cold UK waters.

I would ask yourself the followng questions:
How confident are you at dealing with ANY problem that may occur, have you had to do any problem solving on the unit in anger?
Do you know what your bailout strategy will be, and have you validated that it'll work, and be correct for the dives you're planning?
Will this dive be similar (depth, duration and deco loading) to the dives you've done on OC trimix?
Will you be diving with another diver who has knowledge of CCR buddy procedures, or preferably is on CCR themselves?
Will you be diving the unit in a configuration that you have dived shallower (amount of additional kit carried)?

If you can answer "Yes" to all these questions, then I'd be more confident doing the dive on CCR, if you have a "No" or two, then I'd seriously think about doing it on OC, and spend some time over the winter developing those skills.

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