You can build the top normally - rotated at the waist to your liking. This is the end result:
The broadside ends up in a pose that makes him appear to be charging towards the enemy. Sure broadsides have heavy weapons and shouldn't be moving much - but I have had to re position them many times in game to get side armor on a tank(don't forget marker lights allow you to improve the bs of snap shots!). Most importantly though, is now we have a broadside who looks different than the other guys in the squad.