But I prefer a different tweeter technology if you want an
extreme ultimate system. I don't even like the system design goals,
ie operating the driver down to a few hundred hertz. While this
is a great DIY project, be open to it's limitations.

Some of the specs that interest me are average, ie 1/2 Tesla gap
plus "According to Linesource's effeciency formula, they will be
right at 98 dB/W with 8 micron foil". This is boring specs.

You can find affordable commercial ribbons with 1T gap and higher
sensitivity right now. Plus, if you do parallel elements and can
live with a line array vs. line source, as low as 1.5khz - 2khz
crossover point, it would beat out this project pretty badly.

Last, I would never use low powered amplifiers to drive an ultimate
sound system.