Have recently been told that sharpening kits (i.e. Gatco) with angle guides and clasps are only suited to 4 inch blades or less. Anything greater than this, the clasp has to be moved along the blade mid sharpen.
Yes you're right but as long as you overlap your 4" sharpening arcs by an inch or so, you can still get an evenly razor sharp result. Unless you're sharpening your sabre, two arcs should cover most blades. The Gatco sharpening kit is excellent and if you have a knife fetish you really should get one.