Here is my saga with cylinder re-sleaving and Dot 5 silicone fluid.
I rebuilt both my clutch and brake hydraulics a couple of years ago using silicone. Since then I've never had a problem with the brakes, but had to rebuild the clutch master a couple of times.
I replaced the clutch master but after a couple of months, the clutch started to "stick" when you were engaging it, causing some jerky take-offs. It was suggested to me that it could be a problem with the throw-out bearing assembly binding as it slides up the shaft. But before pulling the tranny, I thought "go back to the last thing fixed". Sure enough when I examined the clutch master, it was evident this was the problem. The piston was jamming in the cylinder and had scored the bore (these are alloy units unlike the steel break master so easily dammaged). So I honed out the old one and put it in (hoping it would hold, even though it was a little pitted, and since it was silicone fluid, a leak would not be a disaster), re-bled the system and was fine again for a couple of months.
Then the same thing started again - the clutch sticking. Pulled the master - same cause. So at this point I called Apple about a re-sleve in stainless or brass.
They told me that 1) they could do either, but stainless would wear the seals faster, and 2) silicone fluid "causes the seals to swell", and that was what was causing the piston to jam. Neither of these really rang true with me. The break master is steel, and I have not had anny issues elsewhere I used silicone fluid
So after considering the options I decided to go with the stainless resleve. I reasoned if Apple were correct and the seals were swelling because of the silicone, the stainless would wear them down. If Apple were wrong, I'd be fine too.
Its been almost two years, and no problems. The clutch hydraulics are smooth and leak free. As for no warentee with the silicone, that doesn't really worry me. The cost of a new kit is probably less than the cost of shipping the master to Apple and back. And if you rebuild it yourself, you can see what went wrong.
Rob.