Success!

Both speakers printed.  They sounded pretty good without any equalisation, though around 10 kHz there's a little more harshness than desired.  But that's nothing to do with the transmission lines.  It's the drivers themselves.  Below is a set of plots of the response curves:

The blue plot has much better flatness than the original speakers.  A little ironing with Eaualizer APO and they're great.  I did attempt to meddle with the crossover, but that can of worms requires swapping in and out lots of capacitors and inductors.  Using a DSP is much easier.  Besides, the crossover had correct phasing, any meddling could have crippled that.

Now to draw up and print some stands and I'm done.