Stuart:
No need to apologise for contributing to a discussion on iron sights. You have raised a very valid point, one that Ross Seyfried published an article on years ago, although in your case I believe you would be better-off with a platinum insert, so it will still be there after you have pushed through a brushy gully!

Coming from a highly successful pistol-shooting background, Seyfried realised that the standard pistol 'iron' sight, consisting of a deep square notch and flat-top blade, operates like a peep-sight. The shooter does not focus on the rear sight, just the front sight. The wide deep rear notch is there simply to provide a light-gap on either side of the front blade, in the same manner as an aperture sight.

Seyfried set this sight up on an early Remington .416 rifle from memory, and guided in Africa with it for several seasons.

OK, so why not just 'go the whole hog' and fit an aperture? The pistol-style irons look more traditional in their position on the barrel I guess, and are a bit of a hybrid in that they can still be used as a precision sight by bringing both the front and rear sights into focus, if you have time.

Anyway, I shoot pistols myself, and quickly recognized the merit of this sighting system. Although I have never fitted-up a rifle that way myself, I have always kept it in mind, and it may suit other posters here as well as yourself, Stuart.

PS: to get the best out of this system, you would need to widen and deepen the rear notch on that Martini I reckon. The depth could be 3 or 4 times as deep although I realize the sight body might not permit this. Ideally it should be wide enough to permit a light gap in the order of 1/3 to 1/2 the width of your front blade, on either side.
Anyway, food for thought......