Thanks folks! While I had looked at Satin before (as an effect) it never crossed my mind that someone would include Dolby decoding in a tape emulator, so kudos to u-he. Thanks also S-EH for the link to that discussion … where I got the idea of playing the file back out to a cassette with Dolby off, then redigitizing it but with Dolby B back on!
The best results however were obtained with the excellent DDi Codec desktop application. While it does have a VST version, the extra tweaks available in the app are pure magic. The effects seemed subtle at first, and it took me a while to train my ears on what to listen for, but the difference between the analog transfer (with more degradation) and the processing done though DDi Codec is well worth it, in fact I’m blown away by value this software represents.
I was able to load my source file (the digitized tape without Dolby B processing), audition it within the application while trying to find the optimum calibration, I could adjust minor imbalances (stereo balance, and the wonderful pseudo-azimuth control) and save to a new file for further editing in WaveLab.
Next stop: to check out NAK T-100 (a function generator, oscilloscope, frequency meter and a wow-and-flutter meter and more for 25 bucks!) – thanks for the tip Thomas!