Bicycle Mechanics - Trim on a 105 Front derailleur

I have a compact double with Shimano 105 STI. I am finding to hard to dial in the trim on the FD. I have tried BF searches, Park Tool and Sheldon. But I am still confused. The 105 STI seems to have 4 stops for the two rings. Triples seem easy to index with trim. L-trim-M-trim-H However I am lost with the double.
Should it be L -trim-trim -H or just the first three stops L-trim-H.
Have pity on me.

I have a compact double with Shimano 105 STI. I am finding to hard to dial in the trim on the FD. I have tried BF searches, Park Tool and Sheldon. But I am still confused. The 105 STI seems to have 4 stops for the two rings. Triples seem easy to index with trim. L-trim-M-trim-H However I am lost with the double.
Should it be L -trim-trim -H or just the first three stops L-trim-H.
Have pity on me.

Make sure your FD is properly adjusted first, then worry about the trim problem.

http://www.parktool.com/repair/readhowto.asp?id=75

Same setup on one of my rides.....

If your 105 shifter is a newer 10 speed one, it’s possible to set it up to work on a triple or a double.

Contrary to the Shimano instructions (they call for the middle-trim-high clicks; I couldn't get it to work)....I use the L-trim-trim-middle clicks, & lock out the next trim and 'high' position of the front shifter with the outside derailleur limit screw. There’s actually a ‘down-trim’ coming off what would be the middle ring position on a triple, so you can get a half-click to move the derailleur in some off the inside of the big ring, but I don’t use that one much.

Do the 'normal' procedure...start with the front shift cable loose, set the inside edge of the front derailleur cage just barely inside the chain when it's on the small chain ring on the front, big cog on the back with the inside limit screw, and then snug up the front derailleur cable and start tightening it up (turn barrel adjuster counter-clockwise) until a clean shift to the big ring can be made, and then set the outside limit screw so the outside part of the derailleur cage is just clear of the chain when it's on the big ring on the front, smallest cog on the back. You should already have the outside limit screw in the ballpark so the derailleur won’t over-shoot the big ring. That way the front derailleur is stopped before the front shifter can get to the next trim click or the "H" click.

It's a bit tricky to get it, but it works OK after it's dialed in. I can get about 7 out of 10 of the rear cogs on the small ring and 9 of the 10 on the big front chain ring with out trimming.

Also, to get clean up-shifts, I set the height of the outside of the derailleur cage ‘real close’ above the big ring as it clears the big ring. Somewhere on Sheldon Brown’s web site, he said to keep that clearance as low as possible to get good shifts. I just checked mine and it’s less than 2 mm at the front of the derailleur cage just before it starts to curve up.