I took an STI apart once after I totalled it in a crash. I would have to say the answer would be no. The shifters are a can of worms and probably can never be put back together without damaging something internally.

The Ultegra 6510 shifters are actually used for both the double and triple setups, so I would imagine using a triple 105 on a double chainring probably is not a huge stretch. I'm not sure what Shimano did to the 6510 and if the same applies across the board. Most shifters have a trim feature in the middle of the shift cycle to allow the rider to remove the chain rubbing noise against the front derailleur when the rings and cog are near crosschaining.

I converted my wife's Ultgera triple to a compact double. I set up the triple shifter without any problems on the double chain ring.

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Suffer Well.

Shift into the small chainring. Set your outer limit so that the derailleur doesn't move past the outer ring. I'd speculate that you started by shifting into the big ring, then setting the inner limiter (which still allows the shifter to click-down into what would be the inner-most ring in a triple chainring setup, thereby giving you an extra click each way).

My Ultegra 10sp requires 2 clicks. From the small ring. the first one seems to be for using the small cogs and the second for the big ring. From the big ring it is the opposite.

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Dick

Take everything I say with a grain of salt. I know nothing.