LG G5 55” with Sonos beam wall mounted HDMI length

I’m getting a G5 55” this week and it’s going to be wall mounted with a Sonos Beam underneath it. I assume I want the shortest possible cable length but can anyone give some guidance on what length would be best? I’d like to order ahead of time if possible!
The beam will sit a few cm below the G5, I’m hoping someone has a similar setup and can advise!