Ok here goes
i
took my 2012 Fatboy apart to install custom swingarm
i went to relocate the BCM but noticed it has to remain in its factory location. Unfortunately I don’t know where that is and the new swingarm changes things
does anyone have pictures of theirs or possibly a page from a service manual

 

You can unbolt the oil tank and rout the wires down so it mounts up behind the rock guard. This will eliminate the need for an ecm tray. You can also get a shorter battery and move it on top of the battery.

 

Is there a certain position it needs to be mounted?

 

sorry, i miss read your post, i thought you were taking about the ecm. my harley is old and it is not equipped with a BCM rather a TSM

 

Yes it needs to be placed like a book flat on a shelf or it will give tip error.
Thanks
AlanD