Ultegra 10s triple STI with double crankset?
Im looking for some info about what components I actually need to upgrade.
My in-laws got me some ultegra triple 10s STIs to upgrade my geared bike which is currently a double, mostly 105, 9s. If I put a 10s cassette and 10s chain on the rear can I keep using a 9s rear der and 9 speed DOUBLE front der and crankset? I have attempted to do this but cant get it adjusted (excessive rubbing at the front and wont get the biggest cog in the back). I dont know if that is because I have no experience with der adjustments and should take it to an actual mechanic, or I must get a new rear der as well as a new front der and new triple cranks and bb.
Can the triple specific ultegra shifter be adjusted to shift a double effectively? And have I properly understood that the range of the rear der is the same for 9 and 10s and so since the indexing is done by the sti the 9s rear der is fine?
Any info will be appreciated. Searching for clarification has left me a little confused. Im sorry if this has been well covered before.