The issue is not whether we should do deep stops, but that if we decide to, then at least have a dive computer that provides us with that option or facilitates the process. Something as simple as adding seconds to the minutes in the dive time would be hugely helpful in tracking the deepstop.
It is a man-machine interface problem.
Right now, the dive computer controls your profile ONLY if you are into mandatory decompression. You apparently want the dive computer to give you guidance on option non-mandatory stops.
One possible way (and IMO the optimal way) to do this is to have the conservatism of the computer user adjustable
during the dive.
Then you would simply start cranking up the conservatism until you get the stops you want. This would be most effective in a computer that implements a true dual phase model such as VPM or the full RGBM model, or if the conservatism is implemented using gradient factors on a neo-Haldanian model. All of those models would generate deep stops as you crank the conservatism up to unusually high levels. This would not work well in either straight neo-Haldanian or neo-Haldanian emulations of RGBM such as "Suunto RGBM" as they will generate mostly 10' and then maybe a 20' stop even as conservatism is cranked up to ridiculous levels.
Or you can just fudge it and add whatever additional conservatism/non-mandatory stops you want. As you pointed out, the key feature to assist in that would simply be to show dive runtime with seconds resolution. Another potential aid would be to add a stopwatch type function.
As with all man-machine interface questions, it is a tradeoff between having a few simple to understand features vs adding additional features at the cost of making the device more complicated to use and understand.
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My personal ad-hoc way of generating deep stops is:
1. At the start of my final ascent, choose a Total Ascent Time based upon my overall loading, water temp, exertion levels during the dive, the phase of the moons of Jupiter and any other miscellaneous conditions.
2. I split my Total Ascent Time between 3 stops. More specifically, I figure out when I should depart the "deepest stop", the "middle stop" and depart the "shallow stop" (in other words, at what runtime do I intend to surface).
3. In keeping with looking at what happens in various deco programs, I choose to make the shallowest stop about 1/2 of the total ascent time, and split the other half between the "middle stop" and the "deepest stop", with the deepest stop being a bit shorter.
4. The shallowest stop always starts at 20' and slowly slides up to 10' (or a bit shallower from a shallow dive). The deepest stop is somewhere in the 40' range (if starting my final ascent from 70 or 80' and shallower) or around 50' if starting from 120' or shallower. The middle stop splits the depth of the other two stops (in other words, it will be anywhere from 25' to 35' depending upon the start point of the ascent).
5. I ignore the maximum depth of the dive. My dives are often very multilevel. For the purposes of my final ascent, I ignore the depth I was at 1 hour ago and look at the depth over the last 10 or 15 minutes to determine the depth of my first stop.
My dive computer doesn't have a seconds display on the runtime. I get around that by picking an whole minute runtime for my departure from the deepest stop. The departure-from-stop time reflects both the time for a 30fpm ascent and whatever stop time I've chosen for the deepest stop --- typically 1 to 3 minutes. In practice, this means that my deepest stop is extended a bit.
The above description is much more complicated to type out and read than to actually do. In practice, the only two things that you really have to remember are 1) runtime at the start of the ascent, and 2) the total ascent time you have decided upon. Keeping those two things in memory is all that is needed to recalculate things as you go along while keeping yourself on what IMO is a near optimal ascent profile.
