Old Smokey, mate .... have I got a deal for you ...
Have a look at doing reverse calcs on the STODA data .. dead simple trig .. although the slope intersections have a bit of scatter due to the round off involved in transforming the obstacle survey data to EOL data ... generally you can identify the STODA critical obstacles to more than adequate accuracy for the requirement ... and, then your problem goes away. (As an aside for a giggle .. the difficulty comes with roller coaster runways ...)
But, why bother ? .. just give the surveyor a ring and ask nicely for the obstacle data ... can't recall the last time I got knocked back or charged more than a nominal amount to cover direct expenses. And, of course, one always drops in to say "hi" and buy the good folk a beer when one is in town as a way of saying "thanks".
Type A aerodrome folks sometimes tend to be a bit more mercenary as they need to recover the cost of the Type A work.
In my view, while you are being less conservative than the sledgehammer approaches of either bringing the first segment distance into the TODA/STODA or matching first segment gradient to the EOL surface ... you are being more conservative than is warranted in those cases (most) where you can do a sensible reverse analysis.