Hitch should be mounted directly or forward of center line of rear axle.
The idea is for the pin weight to be carried by the rear axle.
With a longbed you will have roughly 4' of open space in front of hitch (between hitch on cab)
BUT anything place up there needs to be no higher than the bedrails as front of 5vr will swing into that area when turning corners, maneuvering trailer.
Behind the hitch you will have roughly 2' of open space (between hitch and tailgate)
BUT anything you place back there will need to be lower than bedrails as 5vr pinbox will be swinging back & forth in that area.
I have an enclosed generator (inside an insulated aluminum box) in front area.
It is even with bedrails.
Between it and the hitch is where I carry a 35 gallon tote
Behind the hitch I have a low profile tool box. I can open the top with 5vr hooked up.
This is very similar to the way my bed is set up......
If I had to carry 4 bicycles I would consider placing 2 of them inside the 5vr and 2 of them on a pin box hitch. Only 2 because I would not want them to extend very far forward and have to worry about truck cab and bikes making contact
I would only consider a rear bike hitch IF trailer hitch/receiver were a factory option (or built/designed by a competent welder----like my Dad was) and the bike rack was of real high quality/strength and had a means of adding straps to minimize bounce/shaking back & forth