The bolt holes in the plates are not located correctly. The tapped holes in the cylinder head cover are centered on the opening, but the mounting holes in the plate are offset slightly, resulting in the the plate overhanging one side and not covering the flange enough to seal on the other side. Flipping the plate confirms this, as the misalignment follows the plate orientation. This renders the plates unusable, because they do not overlap the narrow flange enough to seal. See attached photos.
They would also be better if cut from thicker material, as they are less than 1/8", which will not maintain very much clamping pressure on the gasket near the center. After returning these, I made my own out of 3/16" thick plate, but 1/8" would probably be sufficient.
I really wish these were better made (correct shape and min 1/8" thick), as it would have saved me the trouble of making my own by hand. With these improvements, they would be great. I hope these changes are made for future buyers.