OK, so just connect it up and try it.
You don't have to install the thing into the van.
Just lay it out on the floor and connect it up as supplied, test it to se that it works.
Then, try extending one of the sensor cables and see if it still works.
If it does work, try extending all of the sensors, if they also work ok then you are good to install it in the van.
If not, then you need a different kit.
Just do it.
You are suffering from analysis paralysis.
JimB
PS, analysis and design reviews in your head are good.
But sometimes you just have to try it and see what happens.