Interesting stats - I recall looking at this before (maybe with RR?). Reckon there has to be 50,000 plus types and another few thousand projects. I had a look through a book I had on 1930's aircraft - out of that book of the 100 aircraft it contained, 4 had been posted on SC. Some were of course perhaps too well known, but there had to be a good 50 that are worthy challenges. In short I don't think we need to worry about running out just yet - it may just take a little longer to find them!