Thank you for your replies.
I am located in Michigan, the airport is Mettetal 1D2 with a field elevation of 696 ft..
Personally, I want to be by the time I reach the end of the runway 50 ft. high + 30% of the distance mentioned in the POH.
The POH I found on the internet seems to be from 1966. If I interpolate the number for a really hot day at sea level and at max. gross (100°F, 1,760ft.) and at 2,500 ft. (90°F, 2,305 ft.), the take off distance over a 50ft. obstacle, at our airfield, would be around 1,950 ft. Even if I add 30%, I would only slightly cut into my personal safety margin.
Given the fact, that this is a worst case calculation, as it is usually just my wife and me + camping gear in the plane and as it is very rare that it gets this hot in Michigan, I would think that we could safely operate a M20C out of this airport.
This is, of course, unless the numbers in the POH are as much off as those for our O-300 powered 172...
Edit: Interestingly, Mooney states the exact same number on the 200 hp M20E POH.