Sunny
There is no doubt the cause of your near accident was pilot error. I think the best course of action would be to have a quiet talk with the pilot and operator to have his C210 SOPs sorted out before he kills himself and all others on board.
Some where he has listened to bad advice or has taught himself bad habits. Some on this thread have stated that 60K is ok for T/O speed. It generally is but it is NOT for climb out speed. At 72K a C210 will climb very positively and safely. The further you fall below 72K the worse the climb becomes till eventually they won't climb at all.
All C210s need about 2,000ft (600M) to clear a 50ft obstacle at gross weight and perfect conditions. The Turbocharged C210N has the longest requirement at 2,160ft (same wing but 4,000lb gross wt)
Referring to the "fright flight" there was 3,500ft of useable runway plus 600ft cleared of trees. This gave the pilot in excess of 4,000 ft to clear 50ft trees.
Using the 10% reduction in effective runway length per degree upslope rule of thumb we can calculate that the 1.6 degree upslope would reduce the effective length by 16% ie 640ft leaving an effective runway of 3,360 ft.
Even a fully laden T210N would have had 1,200ft spare for unforseen variations in conditions.
Had the pilot used any climb speed above 72K the departure would have been stress free and the seats clean for the next flight.
If I've learned anything about C210s over the last 40 years it's that you don't take off too slow and you don't try to land them too fast.
Cheers RA