I would not carry bikes in the bed of a truck with the hitch installed and the 5er attached.
I carry a storage box ahead of the hitch, but below the top of the rails so the 5er will clear the box. This is for tools and grease and such. I also carry the king-pin stabilizer tripod along with the planks for the trailer tires to sit on when set-up.
That is about it.
Jim & Jill
Sold: 2010 318SAB Cougar:New: 2016 Cedar Creek 34RL. 2008 Dodge 6.7LCummins the original 6.7L engine, w/68RFE Auto