Getting the right cockpit position. Sliding forward. What should I adjust to keep my sit bones on the seat? I am experienced rider and I'm looking for some advice on how to adjust my cockpit position. I am a daily commuter, and do regular 40-50k rides on the weekends, and with the warmer weather will work on some 100-200km rides. 

On my current bike, I continue to have a problem sliding forward in my seating position. I have short arms and legs compared to my body length (32 inch / 81cm inseam at 6'1"/185 cm tall) and my bike is fairly comfortable if not one size too small. The bars are currently about 2"/5cm below the hieght of the seat. I find that I am consistently sliding forward my seat and pushing back with my arms to stay in a decent position. My saddle is currently pushed as far forward as the current post will allow, and the stem that came with the bike is quite long. The seat post off-set is not large at about 1". The Brook saddle (B17 Special) is dead level as measured at the rails. I have no knee or back pain.

What should I adjust to keep my sit bones on the seat? 

I think my options are:


Shorten the threadless stem to xx cm or so from the current 120ish?
Buy a new seat post that will allow the saddle to come forward more?
Buy a new bike that fits better (Probably not going to happen this year)? 
Other? Seat height? Seat angle? 
Stretch more? and get a flatter back, better hip position?
Try changing the seat angle. I'm tall as you, and had the same problem. I changed to a bigger frame, but the real solution was to set my seat a bit off the horizontal (back is lower than front). Seat and handlebar are at same height. No more sliding.