The bridging plan never happened, but I did use one of the amps in stereo mode extensively, comparing triode to standard sound. Let me tell you, those EL34's, run in triode mode, were a revelation. I've never heard anything so "real," tangible and tactile as that.
I also tried KT88's (I think that's the model #) tubes in this amp, and that was interesting: they sounded a little stronger & more impactful, but a touch less "real," than EL34's in standard operation; and they sounded weak and strangled in triode operation (that experiment didn't last long).
I still have the amps and all the tubes in storage.