Roadrunner: Could you post a picture of what your saying. I just bought an outback and haven't tried it out yet.
This does not apply to standard fins, only to ST and ST Turbo fins. In the picture below, the clew outhaul is highlighted in red. You want to adjust it so the top edge of the fin tucks into the plastic outhaul block about 1/8" as shown. Compare this with the earlier pic showing the fin tucked in more or cinched up. The Green highlight shows a gap at the top of the leading edge of the fin (provided the mast is not bent). As the fin twists it develops its "pitch" (just like a propeller blade) by winding up the mast. This is where the thrust comes from. I look for about 1/4 to 3/8" play as a double check on the clew outhaul positioning. If this gap is closed, the fin can't twist as much and becomes harder to push, delivering less thrust.
Is there a recommended List of parts to have on hand. Like the 10 top selling parts. I'm a little nervous about drive failures on the open water.
Personally I don't recommend wasting time carrying spare parts unless you're on an extended trip. Murphy's law says no matter what you carry, something else will break. It's also extremely difficult and risky to attempt repair while bouncing around on the water with wet hands -- your tools and parts may end up overboard. Not everyone agrees on this philosophy though.
A little known fact is that you can break a lot of parts and and the Drive will still work. If something breaks most people assume the drive no longer functions and they get out the paddle unnecessarily. You can have one fin fall off, any one cable (sometimes two) break, and the Drive will still get you home. Here's a link with more detail:viewtopic.php?f=11&t=8240
(Sorry, some of the images seem to have disappeared over time, but you should get the idea).
IMO, the best policy is to frequently inspect, lube and adjust your Drive. Most problems give warning well before occurring. The only difficulty is knowing where to look. This comes with experience in many cases. Again, most users just use the Drive without inspection until something breaks. I've done that as well.