So the build plate sags on the four corners. To fix this I ordered the Ender Extender Ultimate Y Axis upgrade. It comes with a bigger carriage plate, two 2040 400mm profiles and hardware to use rollers. There is no guide or instructions for this. So if you get one you’re kinda on your own.
Since I already swapped over to use linear rails I wanted to keep using them. The new carriage has mounting points for the linear rails but each side requires two baring blocks. So I have two more baring blocks on order, some m3 washers as spacers and 2040 L brackets.
I’m going to create a build guide for my setup of this Y axis upgrade. So if you end up getting the Y axis upgrade you might just want to buy the carriage and not the whole kit.