Raymond;

I have to agree with those suggesting an adjustment problem.

Here's some advice for locating which corner the "lost motion" is on: Has a helper slowly push the brake pedal while you check for drum drag at each corner one at a time. I expect the corner that the fluid is going to, which has the extensive free travel on the shoes will be noticibly free-er while the pedal is moving...and naturally, once the pedal is hard, all drums will be locked, so you need to coodinate well with the helper.

Your explanation sounds very much like the effect I notice on my 122's rear drum shoes, as they wear...the pedal goes lower and lower before firming up, but a click or two on the handbrake (which essentially moves the resting position of shoes closer to contact - sort of a manual adjustment from the drivers seat) results in the pedal being nice and firm up high again. When I notice this, I just keep the hand brake clicked up those two clicks until the next opportunity to make the proper adjustment down at the drums.

In your case, if you notice this effect with the handbrake also, it narrows the problem down to the rear end of the vehicle!

Good hunting, please let us know what you find.