Update: Finished the build, ended up finding some RL721's for cheap. After a lot of shimming, I managed to get everything on the bars. The cable pull on the levers isn't actually stopped by their construction; rather, their travel is limited by when the lever strikes the bar, so on an outside curve they could conceivably even pull more cable than a mountain lever. On a flat segment of bar (such as the top of a drop bar), they pull less cable than a mountain lever.
When I first set them up, they were understandably spongy, but after dialing in the brakes/barrel adjusters as close to the rim as possible, the stopping power is excellent for my needs. The top levers are extremely powerful as a result, and catch the rim almost without any pressure.
Verdict: If you're anal about truing rims and adjusting brakes, inline levers will work for you.
(Note: I have not yet adjusted the reach on the top lever, I don't have freakishly large hands as the image would suggest)
