It's obvious that I need to get a life ...

I've just built a TCWSCONS-based install kernel, both to make it easier on
myself and to prove it could be done. It's REALLY REALLY untested. It may
sexually assault your pets, for all I know, so be careful with it. :) I've
netbooted it, and just plain booted it from the root of an existing
install - and it seems good. What I haven't done is tried it out as part of
a cdhdtape image.

That said, you can get it at

ftp://discord.maths.monash.edu.au/pub/netbsd/tcinstall.gz

There's also a modified kern.tgz file in that directory that you should drop
in to your 1.5 binary install set - it's not a stock TCWSCONS kernel, but
it's the one I use on a daily basis and has never given me any problems.
It's also the home of the patched SFB X server binary. All in all, it's
probably a very interesting directory for 3000 owners. You should be able to
go from nothing to X without using a serial console.

If someone who is not me could verify that it works, that would be great.
It's all built from stock 1.5 release sources, except the X server.