Pete, I believe the TD flat spring action info is in one of John Campbell's books, probably the first one.

It's my personal belief that Winchester used more overtravel than necessary in order to ensure that no unsafe rifles left the factory. Although the walls were made 'to gauge', there was/is still enough variation so that I have observed a definite difference in the amount of overtravel in the course of examining a number of rifles over the years. For this reason I believe the factory increased the amount of nominal design overtravel so that the tolerance spread wouldn't cause problems. I can't figure any other reason for such an obvious glitch in a John Browning design.

Karl, Many M-N conversions have the longer safer f/p's, not all are the floating or inertia type. And you're right, the link must be modified to retract the hammer, de Haas shows this very clearly in several of his books. He also describes a very practical and straightforward M-N conversion, for those who prefer it.

The British action you describe sounds like it would be fine for the 44-40. But don't sell their system short, the hammer-with-integral-firing-pin system can be made almost as gas-tight as the separate f/p type. I have a Westley Richards boxlock double with this type f/p system (made in 1883!), and the f/p noses are an extremely close fit in their breechface holes, certainly snug enough for any of the medium-pressure rifle cartridges like the 30-40 or 303 for instance.
Good luck with your project, Joe