OS,
Missed the chess move .. unless it was the reference to the large carrier ?
Used a similar approach for a while but gave it away for one-offs in preference to the G1 or D1 sledgehammer techniques for simplicity .. and comfort (mine) ... this sort of analysis can be beset by differences of small numbers problems ..
In any case, use of this approach would normally be by means of a standard STODA/TODA correction in the ops manual so there should be no need for the pilot to do other than apply a declared (albeit conservative) correction for the particular Type/configuration ?
A few thoughts/questions ..
(a) I presume that you address the H3 problems by some other rational means for crew use in the field ?
(b) What is the rationale for your running with a 0.4 margin on G1 ?
(c) You could also consider simplifying the expression and procedure a little by replacing
180 - A - S1A
with the equivalent
180 + runway slope - STODA slope
which might help a bit with potential differences errors.
Re TORA and TORA+60, pragmatism dictates the latter, but from a regulatory viewpoint, I would want Regulator concurrence otherwise I would go for the TORA declared value.
Isn't this all jolly good fun ... ?