You might want to think about doing that dive on 27% instead; I'm happier with the PO2 with that profile.....
Try this on for size...
V-Planner 3.30 by R. Hemingway, VPM code by Erik C. Baker.
Decompression model: VPM-B
DIVE PLAN
Surface interval = 2 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2
Dec to 140ft (2) on Nitrox 27.0, 50ft/min descent.
Level 140ft 27:12 (30) on Nitrox 27.0, 1.41 ppO2, 127ft ead
Asc to 100ft (31) on Nitrox 27.0, -30ft/min ascent.
Asc to 70ft (32) on Nitrox 27.0, -30ft/min ascent.
Stop at 70ft 1:40 (34) on Nitrox 50.0, 1.56 ppO2, 32ft ead
Stop at 50ft 0:40 (35) on Nitrox 50.0, 1.26 ppO2, 20ft ead
Stop at 40ft 3:00 (38) on Nitrox 50.0, 1.10 ppO2, 13ft ead
Stop at 30ft 4:00 (42) on Nitrox 50.0, 0.95 ppO2, 7ft ead
Stop at 20ft 19:00 (61) on Nitrox 50.0, 0.80 ppO2, 1ft ead
Asc to sfc. (61) on Nitrox 50.0, -30ft/min ascent.
Off gassing starts at 91.3ft
OTU's this dive: 75
CNS Total: 29.2%
112.6 cu ft Nitrox 27.0
32.7 cu ft Nitrox 50.0
145.3 cu ft TOTAL
(I set last stop to 20', as holding a 10' stop in a 3-4' sea is a real pain in the butt. 20' is much easier.)
If you prefer 80/20, then try this on for size:
V-Planner 3.30 by R. Hemingway, VPM code by Erik C. Baker.
Decompression model: VPM-B
DIVE PLAN
Surface interval = 2 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2
Dec to 140ft (2) on Nitrox 27.0, 50ft/min descent.
Level 140ft 27:12 (30) on Nitrox 27.0, 1.41 ppO2, 127ft ead
Asc to 100ft (31) on Nitrox 27.0, -30ft/min ascent.
Asc to 60ft (32) on Nitrox 27.0, -30ft/min ascent.
Stop at 60ft 0:20 (33) on Nitrox 27.0, 0.76 ppO2, 53ft ead
Stop at 50ft 3:00 (36) on Nitrox 27.0, 0.68 ppO2, 44ft ead
Stop at 40ft 3:00 (39) on Nitrox 27.0, 0.60 ppO2, 34ft ead
Stop at 30ft 3:00 (42) on Nitrox 80.0, 1.53 ppO2, 0ft ead
Stop at 20ft 13:00 (55) on Nitrox 80.0, 1.28 ppO2, 0ft ead
Asc to sfc. (55) on Nitrox 80.0, -30ft/min ascent.
Off gassing starts at 91.3ft
OTU's this dive: 77
CNS Total: 30.8%
122.9 cu ft Nitrox 27.0
16.1 cu ft Nitrox 80.0
139 cu ft TOTAL
For the extra six minutes I'd probably take the 50/50; if something goes wrong and I have to get out early, I will have gotten some benefit of the enriched deco gas. This is, however, pushing the amount of deco gas available in a 40; you do need to be able to deco out on remaining backgas if something goes wrong. That's a fairly long hang if you lose the deco gas though (close to a 90 minute total runtime.)
Of course if I want to do TWO dives then I might take the 80/20 instead...
