Hullaboo,
In fact the ICAO Annexes (6 and 14) defer to the Flight Manual, specifying only in the absence of limits.
My remarks were directed towards the issue of adequate visual reference using '1D' only as a general example. Flight Manuals tend to provide their limitation in specific units of measurement - not in proportions of 'D'.
The limits in the FM are a result of a CAT A certification exercise and so are directly applicable to each procedure (hence the two limits: one for ground level helipads; and the other for elevated helipads).
In the example you use, there would have to be a practical demonstration of appropriate cues on the surface - hence, each helicopter is assessed in its own FOV environment.
In fact the AC 29-2C guidance is not comprehensive enough because it is not the cues at the TDP that are the main issue it is those at the height/position where the aircraft stops its ascent following an engine failure at, or before, the TDP.
JARs are sophisticated in their treatment of size of helipads in PC1; providing it can be shown that there is no probability of a rejected take-off (i.e. the case where a continued take-off is always possible), the CAT A helipad size limits do not apply. This is of most use for HEMS aircraft which are operating to hospitals with historically smaller helipads (smaller than those required for CAT A).
Jim