Martin's answer to the popularity of archtop guitars was their series of arched top models in which R was 00, C was 000 and F was a new 16" body that we now call 0000. They were not particularly successful tonewise and thus now are often converted to flattop. The first conversion was done by Marc Silber and Mario Martello, and that instrument influenced Matt Umanov to build one for Dave Bromberg, who demonstrated to the world the special qualities of this new breed.
Howards conversion is a special creation; he's put his all into it, creating a new/old instrument of the highest order. The new neck is long scale, the quality of workmanship is as good as it gets, the tone is strikingly powerful, rich and sweet. Howard describes the tone as having a beautiful sustain in the baritone regions.) Martin's way of bending the back such that the body is a bit thinner at the heel than the butt may be bringing in some of these special qualities.
Howard has created a thread about this project in the Unofficial Martin Guitar Forum that contains many fascinating details and photos: http://theunofficialmartinguitarforum.yuku.com/topic/131872/F-7-Conversion-by-Howard-Klepper#.T7P1w44qOiY