It's all in the engineering.
IMO, a decent usable implementation of this design depends on
where the flex occurs, how much flex travel there is, and how
stiff the flex action is.
Absolutely, a new model such as I'm proposing shouldn't flex freely, which is why I said there should be a resistance to it. I think a good amount of resistance would be just a hair more than the same amount of pressure used in keeping the HB close to your scalp. For most of your shave, it shouldn't need to flex -just those trouble areas that some of us have.
As to the position of the flex point, it should flex closer to the tail, definitely not directly under the finger ring. And it shouldn't flex very much, either.. just a bit.. maybe 15 degrees?.. just enough to give it a tiny bit of flexibility boost in those tight areas.
I made a quick'n'silly diagram to demonstrate the physics of using a shorter HB versus a longer one.
It's way exaggerated but I wanted to make the point of long vs short.
Naturally, nobody's head is as curvy as this (I should hope!) but mine is pretty knobby up in the front. This is where I have the most trouble.
Obviously the longer ..umm.. "thingy" here is going to have more of a problem getting in and out of all those valleys than the shorter one.
I wish I could've animated it!
The possible problem is, if ya make it
too short, there's not enough distributed surface area and the pressure applied could be too concentrated: a shaver is going to have to seriously watch his hand pressure.
In any case, the fact that many, many users here as well as other sly guys do not like the HB, is to me, a further indication that is perhaps not forgiving enough for everyone; not that those guys are technique-challenged.
Even if I'm wrong about the idea: if everyone always said, "if it ain't broke don't fix it", we'd never have have any advancement in technology or improvement in our quality of life. There is always room for improvement. Just because it works fine for this or that person doesn't mean it works as well for everyone else- not all heads are equal.
Lastly, I wouldn't dare suggest discontinuing the other models, just have the new one and see how it fares.
Granted, I like and will continue to use my HB, but I'm not sure I'll use the Sport.. I'll try it again, but.. I felt like because of the angle forced on it by my head, it wanted to dig into the side of my forehead ridge.
As it is now, I'm using my HB for the top of my head, and some in back, but for the sides and those ridges, I'm using a Sensor or Mach 3. I can just get in there better.