Tubeless with rim brakes...

I'm sorry... the pater familias? Is that STW patois I've not yet come across.

... I have no idea about tubeless and rim brakes. Sorry.

Edit: slightly disappointed there's no Latin here.

Puncture fairy

Puncture **** would be more apt

Rims aren't likely to be compatible - especially the rim joint. I'd just get some better tyres TBH for the job. I rarely get a 'visit' from the 'fairy'.

I run tubeless and rim brakes with no issues at all both on my road bike and my SSCX/Commuter bike with no issues.

You'll probably not even need Stans strips, mine are just taped and valves as normal, just don't run it so low that it has potential to burp.

They're A319s; was thinking of running the pressure as high as I can (40psi?)

No issues with my setup, but then again they are dedicated tubeless rims unlike the A319?

A319's are a pinned rim, not welded, so you are likely to get leakage at the joint on the side walls which you can't tape.

the aero wheels I bought cheap as CRC were going pop were specifically tubeless-ready (as in came with the valve installed) rim-brake-only - so they obviously thought it was ok

Yes, a few rims are rim brake and tubeless ready (DT make quite a few, i.e. R450, R470, R500).

I am running tubeless on my 26" with some non tubeless rims and it works fine (with tubeless tyres)

Tubeless with rim brakes here, both gravel and road.

I wonder if you're thinking of reported issues with rim brakes and latex tubes? Not recommended due to heat build up, although I've survived the Alps and Rococorba with that setup

I would just go ghetto with split inner tubes and proper tubeless tyres. I used to convert all my old rim brake bikes back in the day (using standard tyres and art latex as sealant), the rim brakes don't make any difference.

A319’s are a pinned rim, not welded, so you are likely to get leakage at the joint on the side walls which you can’t tape.

Firstly, most rims these days are pinned or sleeved. Since disk brakes there isn't really much advantage to welding anymore as brake tracks don't need to be flat. In strength terms it's a non-issue because rims work in compression not tension. And welded or not are very weak under side loads.

Secondly, it's not an issue, either

a) stans tape slightly wider than the rim so it rolls up the edge. It only needs to go high enough that the tyre bead rests on it to seal.

b) stans tape slightly narrower than the rim but with a layer of PVC electrical tape on top because its stretchy/flexible.

I prefer B because it means I only keep 1 roll of narrow tape that works over the spoke holes and make up the rest of the width with electrical tape (which is also lighter).

Given that it's not a tubeless-ready bead, is there any mileage in trying to track down CX rim strips (with a valve) or is that overthinking it?

There is a potential risk of the tire rolling off the rim if it suddenly flats. Proper tubeless set ups shouldn’t do this.

If memory serves (used to run DT disc rims with Stan's rim strips in time past) the idea of the rim strips was to provide something for the bead to sit against and reduce the risk of that?

Pre-made rim strips do not perform any better than tape, they're just a simpler consumer item. If you tape it and use a tubeless tyre you'll be fine.

Procurator Fiscal? What's your crime (apart from still using rim brakes)?

I guess it could be an issue when your rim wears through

I have some TR rim brake rims on my road bike (Ambrosio P20) but I choose to run them with tubed tyres still, mainly because Road tubeless tyres are still a bit steep IMO.

I can't see why tubeless would be any more susceptible to failure with rim brakes than tubed tyres...

I use 317 tubeless with just some Gorilla tape with no issues.

So…

Think the Stan’s rim strip I found has perished into a hole at the valve stem base, and there’s a hole in the tyre from aforementioned PF visit.

Plan is to have another go with rim tape and a new valve, and then load up with more sealant unless anyone has any better ideas?