If I can make a suggestion regarding the location of a bike carrier.
You are lucky that you have bought one of the most stable caravans around, but if you are not careful you can destroy all the hard work carried out by the Eriba engineers!
I will attach an image that shows how to load a caravan.
Essentially you want to put any heavy objects as close to the caravan axle as possible and as low down as possible. The very worst place to put heavy objects is high up and at the rear.
The image suggests loading high up at the front is not recommended too, but it is less of a problem at the front (as long as your nose weight is okay) because the car will cancel out much of the pendulum effect, whereas that back of the caravan can swing around freely!
Have a look at this video to illustrate the instability caused by putting heavy objects at the rear.https://youtu.be/PFzrWHTG5e8
I currently tow a white plastic box, which doesn't have the stability of an Eriba, so loading is very important, if not critical.
On my last trip out I pulled over 30-minutes into my journey and moved two duvets and four pillows off the rear bunkbeds and moved them forward, such was the instability I was experiencing on the motorway! These relatively light items made all the difference, but our van is nearly 8 meters long and the back of the caravan is around 3 meters from the axle.
You would however notice a reduction of your stability if you mounted a heavier bicycle carrier and bike at the back of your Eriba.
Your most stable option is to mount the bike or bikes on the car. Best place would be on the car roof between both car axles, but on the back of the car should also be fine.
After that, I would mount a bike carrier to the caravan drawbar, as we have.
Hope this helps.