Heres my current situation. I just upgraded my '08 Sora group; triple crank; 9 speed system to 105 F&R derailleurs matched with an Tiagra 9 speed cassette.

My issue here is that I can get a brand new set of Ultegra Shifters for less than it'd cost for a set of used 105's on ebay.

Would the shifters work properly with the 9 speed drivetrain? Ie would it mesh properly?

I also have a 10 speed Ultegra cassette that I could swap on but then the question is would the 9 speed rear derailleur work if I fiddle with the adjustment screws?

Any help would be appreciated.
Thanks
David