I recently bought a trek 1400 with downtube shimano 105 indexed shifters and a matching derailer and 7speed gear set. It has a spacer so an 8speed would fit.

Well theres the background so I will jump right in it. I hate the down tubes. As a commute bike for school sometimes I have 25 pounds of books and snacks and boots to change in to with me and taking one hand off the handle to shift makes that lopsided weight become suddenly appearent. Also when I wear my winter gloves I can't feel where the levers are so I often over shift and have to come back up a gear. Needless to say, it is inefficient

I got a quote for some 7 speed sti levers and a down tube adaptor and brakeboss brakes for 180. Labor included. I feel like this is a pretty good deal. But a fellow bike and subaru enthusiast who works in a bike shop across the country tells me the low speed sti levers are cheaply made and I should upgrade to 10 or its not worth so much trouble. I was wondering if its possible to make a 10 speed sti work on a 7/8 derailer and gear set until i can upgrade those parts later. Id rather do this in bite sized chunks to see benifits soon instead of saving up for a long while. My friend said I will probably just have ghost clicks, but im worried half my gears will fall between and will shift back and forth constantly.

Also if anyone has done anything like this, or any down tube to sti upgrades, could you let me know of anything I should beware of or any tips in general? I tried searching but didnt see anything about upgrading everything but in bite sized chunks.

Thanks in advance guys!
Ratchet