My Setup is to have two 160x160 panels side-by-side with 80x160 panels. So 2x160mm in height and 240 in width. Though the original design did not fit right between my IVAR posts and I had to trimm down 2mm per panel. My first try using the mounts by u.s.e. ( https://www.printables.com/model/283268-ivar-mount-fur-mini-montagebrett-modular-inspirier ) did not yield in success, so I designed some mounts in OpenSCAD myself as a robust fix.
The provided STL is goes well with the printable IVAR pegs of mine: https://www.printables.com/model/557222-peg-for-ikea-ivar-system-openscad-parametric
You need to print 4 in total, of which 2 need to be mirrored (to account for both sides).
You could even secure the board with a screw, but for me the fit is tight enough.
Full parametric OpenSCAD file provided as always (just download and install the software, open the file and adjust to your needs with the parameters-panel on the right hand side).
The author remixed this model.