Greetings! Intro and looking for advice.

[tggzzz]

No I don't have the facilities to do frequency characterisation these days (sob). The best I could do was parallel measurement alongside Tek P6139A with a 100MHz squarewave logic source on a 250MHz analogue bandwidth scope. I could clearly see waveform distortion on the Zo channel as the Tek probe was attached / removed, but only slight amplitude change on the Tek probe channel when adding / removing the Zo probe.

That's much better than nothing, of course!

Have you considered using RTLSDR dongles that work up to 1.5GHz as a poor-man's spectrum analyser, plus a noise source as a poor-man's tracking generator? My experiments are at https://entertaininghacks.wordpress.com/category/frequency-domain-analysers/

The resistors are bog standard 1k metal film (0.25W)... 20:1 with 50R through terminators. They are socketed so that I can swap resistors as needed.

There's a thread on here about self-rolling probes (I see you get a mention for your EDN article. 

The socketing appears neat, provided the resistors only fall out when you want them to Me a pessimist? Shurely shome mishtake.

For clarity, I'm not the author of the EDN article; I merely linked to it.

[Gyro]

Weel I've got as far as considering the dongles, unfortunately that's as far as I've got so far. It would certainly be a useful addition as my highest frequency source at the moment is 180MHz. Edit: my frequencies of interest iseem to be lowering with age... tracking my hearing, both tending towards DC.

The resistor sockets are culled from a turned pin IC socket (soldered at the body). Removal is a pliers job,  That little bit of PTFE sleeve makes all the difference to rigidity as it supports the base of the resistor, not just the leg.

For clarity, I'm not the author of the EDN article; I merely linked to it.

Ah yes, I realised that when I actually took the time to re-read the thread (which I notice you also had several posts in too). I had only pulled it up briefly to retrieve my probe photo.