I've just finished my modded Wilson II with a width and height adjustment of +50mm.
I did this for 2 reasons and the first being with just 300mm Z leadscrew I only ended up with about 170 -180mm which was a bit of a problem when you started a new print and the Z wanted to raise for the Z probe clearance. Plus I added a smart extra cable routing which reduced it by another 10 or 15mm.
The second was to just get all the 214mm of the Bed in X but also if you accidentally go X0 you end up smacking the Z probe into the bed if you are low enough.
The Z mod was easy enough as I found a supplier with 350mm Lead screws on eBay and X just needed longer 2020 extrusion and smooth rods as well plus a longer GT2 belt.
As I was building a new frame this was not a problem. If you doing an upgrade to an existing frame you need to think about wires as well.
My cutting List:
X 2020 Aluminum extrusion 380mm x3
Z 2020 Aluminum extrusion 450mm x4
Y 2020 Aluminum extrusion 500mm x2 (same as original)
X smoothrod 440mm x2
Z smoothrod 374mm x2
Y smoothrod 500mm x2 (same as original)
In the Config H file:
'#define X_MAX_POS 200- change to 250
'#define LEFT_PROBE_BED_POSITION 15 - change to 40
'#define RIGHT_PROBE_BED_POSITION (X_MAX_POS - 15) - change to (X_MAX_POS - 40)
The only small problem I have is when I slice a file and print it is 25mm off set. which is weird as when I do home and bed level it is doing it on center.
ATM I am just offsetting it in the slicer Simplify3D but there must be a fix in marlin.
I'll add some pics soon.