Peter, I'm afraid the quote below is the best answer I got when I reposted - note the last line about being in good humour!
OK folks, I'll attempt a translation
"I have a concentric hydraulic clutch release slave
cylinder of my own design."...
I know I can buy these things, but I've got a lathe and the ones you can buy are a complete rip off, so I thought I'd make my own...
"It isn't quite concentric and I
haven't built any compliance into it."
I'm not very good with my lathe and the bits I've made don't really fit together because at least one bit is oval and it doesn't fit into a round hole...
"I want to fix this
before it all goes back together and hopefully cure the
squeal from the clutch which was heralding a premature
wear pattern."...
I have to fix this as otherwise my clutch won't work and I'll end up buying the bits I was trying to avoid buying in the first place.
"My only idea is to shave the external diameter on the
piston so it is a loose fit on the bearing and then refit
the bearing on some blobs of silicone sealant. Does
anybody think this has a chance of working?"...
In addition to a lathe, I also have a file. Does anyone think that, if I file off the lobes on the oval bit I knocked up, then gum it all together to compensate for my dodgy metalwork, I'll end up with a working clutch?
To which I think the answer is no.
There comes a point where the concept of a kit car is taken beyond some people's ability to make it a reality. I think that the questioner has reached that boundary.
All in good humour"