jeffpmills

Yes, when you change from triple to double you need to change EVERYTHING.

Front derailleur
Rear derailleur
Bottom bracket
Cranks
Chain

The BB for a triple is actually longer (pushes the entire crank set out) than a double. So, if you're riding double cranks on a triple BB, you're definitely going to have alignment issues. Also, the triple rear derailleur has a longer pulley arm to handle the increased range required to keep tension whether the chain is one the (very) small chain ring or big ring.

Also, the front derailleur is actually what houses the shift notching (which is why you can use STI shifters for both a double and triple derailleur), so that needs to be changed as well.

Sounds like you're on the right track. Changing drive trains is expensive and time consuming.

Jeffrey Miller