Yes, on all counts. However, I don't know how long it takes for the rubber to deteriorate yet but that's not a major problem, as long as people use doors I have a never ending supply. In the meantime I can put some effort into finding someone that makes rubber and see if they have any alternatives. It does of course not have the same swing range as, say, a Vibrola but enough for what I use if for most, which is some gentle swaying to the beat for power chords that ring out, a bit of warbling here and there and a faster vibrato for pinch harmonics. You don't need a lot of range actually for it to sound good, I don't even floor it. I realized this when playing the Kahler and Vibrola, that I very seldom use the full potential of them because there's a limit as to the usability of everything that swings more than a door stop trem above which things just don't sound good (to me) anymore.
I do of course screw the tailpiece on tighter than the height of the door stops natural height to the point where it stays in tune. I'll have to use it for a while of course to do a full evaluation but, surprisingly, so far so good!
If you find that the rubber (I'm pretty sure it is actually a synthetic, which will last way longer) ages, then maybe a couple of stiff coil springs under there instead? But tuning stability should be pretty good because in the rest position it is up against the flats of the posts which is far better than just trying to find its own position against the spring force which the original does.
Yes, I think that's part of its quite unexpected success. I was looking into springs before I went for this option and it seems the space between the guitar and trem is not large enough to accommodate the necessary ones. On the other hand I could be wrong about how much string pull there actually is but in any case, doorstops are easier to come by than strings in this day and age when nobody seems interested in selling anything useful anymore for those that actually like to make something with their own two hands. Also, chances are springs would just leave marks in the guitar body.
I was thinking about making some kind of blade springs but I quite like that fact that it's so simple you only have to manufacture the tailpiece. For simplicity, it actually beats the Vibrola which means I just invented the worlds simplest trem. On the other hand, I'm wondering why no one else came up with it so I'm just waiting for the defects to start showing...