Hmm. I'd wonder if the wheel guards are removable? then you might cut a block of wood as a mounting pad for grinder to shim it higher, and mount CBN wheels in 8 inch. Also, 6 inch wheel would not be too small for a skew, where'd you hear that? Only difference 6 inch vs 7 or 8 inch would be the shape of the hollow grind (which would affect the cutting edge angle, which then could be remedied by a less acute angle?)
If it were me and I insisted on keeping the grinder (as opposed to buying a modern low speed one) I'd look into possibility of removing guards and putting CBN wheels on it - Of course, your grinder's arbor size would be a show-stopper if it was not a standard size.... Since CBN wheels are not subject to breaking apart like frangible grinding wheels, the guards should not be too much of a concern when using CBN (or perhaps they could be modified?) If all I had was a 6 inch I'd not be too concerned about skew sharpening - any problems with the hollow grind eventually could be honed away as you hone the skew to re-sharpen. (Can't imagine trying to use a skew fresh off a 120 grit grinding wheel, it'd get dull so fast.... It is why I never bothered trying skews after discovering that it was near impossible to keep them to a fine edge without extensive honing after grinding, once I got CBN wheels, things went much better)
