Question about Thule Velospace XT 3

Hey
I used to use the Thule Xt3 for VW T4 and now for Ford Tourneo custom. The tilt function can be adjusted depending on how the towbar is mounted. Works perfectly

XT3, as the name suggests, for three bikes, but with an additional rail a fourth, more likely a children's bike, is apparently possible.
We use the XT3 with 2 eBikes, I don't want any more weight ...