How to manually set the head table values

I want to forcefully set the head table values. In the Custom Parameters section of the Masters tab, I can add other values (such as hheaAscender, TypoAscender, etc.), but I cannot find anything related to the head table. I want to set the values for head’s xMin, yMin, xMax, and yMax.

Why would you change the min/max values? They should match the shapes in the font.

What if you get error messages from “fontspector-”? Do these matter or can I fix them in Glyphs or do I need OTMaster?

What values exactly does fontspector complain about?

Most are petty one unit differences, but the others are vertical metrics errors. Is there a way to manually correct them in Glyphs?

Can you be more specific what you need to fix? What are those one unit differences?