*sigh*
Well, i changed to Horz discharge cap, two bad resistors, and the HV cap. it helped a bit, but not much - the HV still drops like a rock at full brightness, the raster still changes size, and does the bloom and byebye thing as the brightness goes up (past a respectable 'peak' in brightness, but not enough width).
I'm aiming the finger at the flyback or yoke. One thing I noticed - there's left side wave from too much drive, AND, the raster 'wiggles' a left and right - maybe 1/8th inch. The wiggle speed's a function of the vert section. Yoke?
The horizontal waveform shrinks ever so slightly at full brightness. At full darkness
I get about 60 volts p-p drive....
I'm gonna try swapping 6BG6s as a last resort - the one in there should be good, though (it worked in the Dumont...)