The reason why I want to scale the 3D models down is because in multiplayer as far as I am aware, when making an environment on a scale of 1:1 with real life the maximum size of the landscape is 20x20km. I’ve tried to make a landscape bigger than that but when I went beyond the 20km bounds the game froze etc… From what I read in the unreal documentation they suggest implementing some kind of solution between the client and server to fake the coordinates or run multiple servers etc… 
I need my environment to be around 30x30km, so I thought if I scale all the models down by e.g. 25% I would essentially increase the landscape size by 25% and that would be the easiest solution, but I’m worried about potential bugs this may cause.
Is the maximum multiplayer landscape size 20x20km or am I doing something wrong?
I also heard that unreal engine has issues with coordinates in multiplayer on a big map if you’re over 6km away from the center of the landscape, is this true?