This is for my NaNoNovel, and they have places on their own site set up for crazy questions like this, but their board has crashed big-time.
It is set in the future, for the convenience of everything I don’t want to have to get into. There is a small (say, 25 people) unit undergoing some special training. Someone is going to be punished by being publicly whipped. (Publicly effective, and they have ways to heal people relatively fast.) How many stokes is a realistic number?
I know this would vary by type of whip and force behind it. I’d much rather go with a very small number, than something long and drawn out–a quick shock, rather that a wallow. My stand-in numbers are 5 strokes as a starting number, ranging up to 12 to 15 for something very serious. Five might mean you need support to walk away, and 12 would require you to be carried away.
Is this at all a reasonable supposition?
Your numbers sound pretty good. This article on Caning in Singapore will give you a good idea of what offense gets how many canes (suitable as a metaphor for a whip).
In the Royal Navy, a dozen strokes of the cat (cat o’ nine tails) was pretty much the minimum punishment. Intensity differed depending on the enthusiasm of the bosun’s mate doing the flogging. The effect varied according to the individual’s stamina; apparently some men just shrugged it off; some made a hellacious outcry. Two or three dozen was a harsh punishment.
Really extreme crimes (like mutiny) could result in “flogging around the fleet” or extreme numbers of lashes (500). Typically these were applied in installments, with the action paused when the victim looked really bad, then resumed the next day.
One interesting point you might want to consider is whether your characters are used to being whipped. If it is a rare occurrence in your created society - or at least, rare for a person there to experience it - then their tolerance will be very low. And you would want to keep the number of strokes low. If, however, forms of corporal punishment are common then your people would build up tolerance to it and would be more able to take low numbers of strokes.
I know i’m complicating matters - sorry! 
Thanks, everyone, for your help. ZZ, that was an interesting point, too. I’m not going to be too graphic, so I think I have what I need.
(Facts do brighten up a story…)