I play with 3 monitors and the HUD is way to the left and right, is there a way to force the HUD on the centre screen?

Sadly, there isn't. I have the same issue and it is quite annoying. Given the history of developer support for triple screen users and the reatively small number who use it I wouldn't hold my breath waiting for them to fix the problem.

It's sad when a game like Warthunder has better 3 screen support over a true flight sim. 3 screen flying is Warthunder is pretty fun, for BoS I stick with one screen.

There has a key command for turn OFF that silly "HUD", who need this?

You can run PLP in windowed mode...this gives a wider FOV with little or no sacrifice to Vert. FOV. Its how I run my setup for now...until/if they fix.