Some pics:

That FD appears to be a generation prior to the implementation.
The only difference, AFAIK is the bolt that retains it to the braze on. You may be able to retro-fit
At the same time, those chain spotters are useless at best and detrimental at worst.
e.g. Often a chain will still get below them and then it becomes almost impossible to get it back out.

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Not sure about the Sram product but I've found the K-Edge to be extremely effective at preventing drops from the small chain ring and have never seen the chain get under one. Initial adjustment is a bit touchy but once done they work great.

YMMV,

Hugh

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Genetics load the gun, lifestyle pulls the trigger.

The chain spotter came with my Force 22 group. The derailleur attachment bolt is threaded on the head side for it to go into. The washer has a little wing on it at well that a bolt on the spotter pushes against to adjust it's distance from the chainring. Barring a different thread pitch where the bolt goes into the derailleur, I can't imagine the new bolt, washer, and chain spotter wouldn't fit on the old derailleurs.

This video shows the installation. May help for a visual.
http://www.youtube.com/watch?v=3A-1QB7fvIs&t=5m18s

If the force chain spotter is like the one that came with my red yaw derailleur if adjusted right it should work fine. My chain has never slipped below the chain spotter, and has prevented a few chain drops.

I have previously used a k edge one and that worked well too.

After some investigation, I realized that the chain drops switching from small to big. This only happens on certain gears (5-10) and only at a certain torque (slow-moderate). Are there gears that you should never switch from small to big? Obviously I suspect that cross chain tension might be a culprit, but on the ten speed cassette, I'm shifting the FD on the 5th. Not sure if I should just scrap the FD and get different one.

It should work in all gears. I currently use old 10 speed Rival and 2013 Red with the Yaw front derailleur. The Yaw front derailleur works better than the old style one. I'm not sure which style yours is. I'm probably going to upgrade my cross bike to a yaw derailleur soon.

I haven't spent too much time on shimano equipped road/tri bikes but many people say the front shifting is better than sram.