If such a beast exists,( warped cover that is) I see no benefit in planing as the gasket area is recessed. However. clamping it to a surface plate & applying necessary heat may normalise it to it's correct position on cooling...
Because it's difficult to keep clean underneath the tank, I have opted with a chromed cover. Some re-paint & some polish, it's up to you...
Dammitt, it looks like I've highjacked an oil thread...
