I know that it is recommended that one shorten his/her stem length when switching to bullhorns. Right now, with my only option being ordering from the internet, how much shorter should I go? Thinking on average. Right now I comfortable ride a 110mm stem with slightly swept back risers (stock IRO stem and risers). Should I go 1, 2, 3, or 4cm shorter?

For reference, the bullhorns I am going to use are Syntace Stratos'.

Danke.