Adjustable stems are good in a trainer, not the road. At least the ones that do adjustable length.

As a rough comparison just tilt your bars a lot to get the drops another 2 cm out, then see what it's like. Do this on the trainer.

Another idea is to go to your LBS and ask to borrow some stems.

Based on your short experiment and report I'd try a 14 cm to start.

You remind me of a friend of mine that I re-fit.
http://sprinterdellacasa.blogspot.co...ive-thing.html

Good luck with the position hunt,
cdr