This is all very interesting reading.
At the risk of being dull & boring, if you want to know whether you'll reach obstacle clearance height by the end of the runway, why not compare TORR with TODR? Most manufacturers provide both those sets of data. Or, if accel-stop is your desired option, why not compare TORR with LRR, again data provided by most manufacturers. This will get you close to the proportions required at rotate speed, which will in turn enable an estimate by (for example) 10kts less than rotate speed.
If my manufacturer did not provide that data, I would find an aircraft of similar design that did have the data and carry the data across. Absolute distances would not be the same, but proportions tend to be similar across types of similar design.
85% by 40% sounds very accurate. Sounds very RAF though (not insulting - RAF pilots being very intelligent people) - many pilots would struggle with the mental arithmetic for that. Two thirds speed by one third distance is more accessible to Joe Street.