At flying school, 70's, the ground engineer told us of his days in RAF and some experimental flying in, I think, a Victor. This was before the use of computers, RTOW tables etc. There was a structural weight calc and 'finger in the wind' takeoff roll calculation. The bosses wondered just what this beast could do for MTOW. They found a runway with only the sea beyond, the a/c had radio contact with ops during the whole test flight, opened the taps and launched. It probably looked a little like the Russian demo. As per military runways they had distance markers down the side, and they called out their speeds as they passed them. I heard there was some puckering of lips and tightening of buttocks and they eased the rumbling groaning metal elephant off the last pebbles of tarmac and into ground/water effect. Wheels were up ASAP. Perhaps it was good job the under fuselage is so boat shaped.
The story concluded with the FE, our instructor, announcing over the radio, about 2-300yds beyond the runway end, with great jubilation & relief, "V2".
Is there not a limit on clearway? Is there not a maximum % of TORA? It's been too long ago and I can't find a quick reference.