I have the Felder version and it does suffer from the parallax effect but it¡¯s close enough for general cabinetry, if i need it perfect (whatever that is) i just use my Starrett combo square set to the xcut stop, of course then you are limited 12¡± or 24¡± depending on the rule you have. In all the cabinetry I have built i have never found it to be a problem of it is a little bit not perfect, furniture and freestanding cabinetry is a different story - I do want that perfect.
