The only one of our Kevlar discs we ever lost was on a guy with a local dunebuggy. he bought the clutch kit from us on a Friday and came back on Monday with the destroyed disc! We were flabbergasted.  He said he had forgotten to install the input shaft seal. Everything was soaked with oil.
       Looked at the disc and all the lining was gone, and the pressure plate and flywheel were gun-blued. Talked to the place that lines our discs and he said that the bluing indicated a VERY hot situation which would undo the bonding on the lining.
       Apparently the dunebuggy started spewing axle oil immediately. And even though he knew he had a major seal problem he ran the buggy like crazy all weekend at the Oregon dunes until the continuous slipping of the "liquid clutch" created so much heat it disintergrated everything in sight.
       We politely reminded him that we do not warrantee dunebuggy parts. He knew he had screwed up and bought an all new clutch kit - plus extra input seals. Other than that incident we have never had a problem or complaint with our Kevlar discs.
       The person who originally said he had gotten engine oil on his clutch disc from a leaky bell housing seal - well, not so. If you watch the path of engine oil when the bell housing seal leaks the oil radiates out behind the flywheel and can't access the disc. Oil contamination of the disc can only happen from the input shaft seal.
       Can we all agree that the input shaft seal is the weak part of the Corvair clutch? (That is assuming that you have a bolted flywheel). So what to do. I am fairly certain that a disc which is damaged by axle oil is a result not a cause. If our Kevlar discs get oil on them , unlike stock linings, they can be cleaned and re-used. But the input shaft seal still must be replaced.
       If you run extreme use you will constantly lose input shaft seals from overheating FAR more than you will ever damage discs. The fix to most clutch problems is to use an input shaft seal that can stand hi temps better than stock ones. Use two whenever you can.
      Although Viton seals are not good for rotating shafts using one in the outer 2-seal application might be better in the short run. The viton crank seal failures being seen have taken a couple of years and a few miles before they show up. In a dunebuggy or racecar there might be access more often to the clutch simply by nature of the application. If a Viton seal only lasts 2 years that still might be better than frying a non-Viton seal almost instantly.
      Our input shaft seals are made of a more modern hi-temp material but when used in race applications all bets are off.