I did an interesting experiment awhile back and I thought it might be an interesting topic for discussion. I put a Model F-style spring & flipper assembly into a upside-down scrapped Model M barrel frame, alongside a Model M-style spring & pivot plate assembly. Then I laid in place a Model M steel plate with blanket and membrane layers in between and temporarily clamped the layers together with a keystem installed for each of the 2 actuator types so I could actuate each switch and compare them.
The Model F-style flipper was not from a Model F, but rather a 3D-printed version from Shapeways that was designed by someone else. It seems like a fairly accurate replica, and I attached a Model F spring to it for the experiment. The results were as I expected; the Model F-style flipper was significantly louder and crisper than the Model M-style pivot plate.
So now I wonder if one could replace the membrane and blanket layers inside a Model M with a thin Model F-style capsense PCB (with no blanket) that could be bent into the required curvature. A capsense controller would be required, and the barrel frame would be loaded with Model F-style flippers. The assembly would be secured using either a bolt mod or screw mod method. The capsense PCB would need to be designed with enough through-holes to accommodate an adequate number of screws, in the same locations as the original plastic rivets.
It may be difficult to design a capsense PCB with a through-hole for each and every original rivet location, but I think how many would be required for long-term reliability would depend on how stiff the capsense PCB is. If thin and flexible enough so as to exert minimal resistance to bending -- and therefore minimum added pullout stress to the screws -- it may be safe to use 50-75% of the original rivet-count, as long as they are evenly distributed across the area of the steel plate.
Of course, another option would be to pre-attach the PCB to the steel plate, bending it into the required curvature in the process. Metal rivets or screws around the perimeter of the PCB could be used, but this would require drilling through-holes around the edges of the steel plate. Not a problem for the determined, I'm sure; bit perhaps a bit difficult for the casual DIY'er. This method would greatly reduce the stress on the screws, so far fewer could be used, making the capsense PCB layout easier to do.
Some means to secure the controller board inside the Model M housing and to provide a cable connection would also need to be implemented.
I think much of the crisper click and feel of the Model F when compared to a Model M has to do with the increased size and mass of the F-style flipper vs. the M-style pivot plate, and also because it smacks down on the capsense PCB with no intervening rubber blanket when actuated. This has been suggested by others, and I agree after doing the simple experiment I described above.
