I've thought a lot about the Martinmods replacement key: I'd do it in a minute if I were close by, but to do it means shipping the horn twice across the border. I wonder if he would sell the hardware to be installed locally?
I make 3 versions of LH table keys:
1. Vintage
2. Vintage Deluxe
3. Contemporary
The Vintage is the same as my avatar, and is the simplest to make/install. It consists of replacing the arms and spatulas of your original LH table keys, giving you ca 1/2" more leverage, better spatula design, and better table placement. For this version, you could send only your keys, if you didn't want to ship your horn.
The Vintage Deluxe, is similar to the Vintage model, but adds a tilting Bb, linked to C#, and an articulated C#. This requires that you send your horn.
The Contemporary, is an adaptation of the Mk6 LH table keys, and looks like:
http://www.woodwindforum.com/forums/album.php?albumid=48
Besides the Mk6-style table, it adds a tilting B spatula linked to C#, and sliding rollers for adjustable leverage and key travel on each R/L linkage. You have to send your horn in for this one.
Martin Intonation: The intonation on Martins is superb (vintage standards) provided, the horn is setup correctly (flat or round resos - no Maestro - and correct key height), the mouthpiece is matched to the horn volume-wise/frequency-wise, and the lower register pip is replaced. Further refinement can be obtained by replacing the cylindrical tenon, with a conical tenon/receiver pair.
This is pretty much the same for all the great vintage horns.
9 years ago, after 35 year on Mk6's, I realized that the vintage American sound was what I really wanted as a player. I sold my 82k Mk6 tenor and bought a #300,996 1948 King Super 20 tenor which was great. Then, about 2 years ago, I heard
John Michalak demo a The Martin Tenor on a CE Winds eBay auction. My stomach got a knot in it and I got goose bumps. That was the sound I was looking for, dark, endless dynamic range that brightens up when you push it, and a zing in the upper register that won't quit. I sold the King, and bought ATB Martins, and have been ecstatically happy with them.