I had a KD-500 for 20 years with a Grace 707 arm. If you don't have an armboard with your Kenwood at all, you could make one if you have a router by cutting a perfect circle out of mdf or a hardwood (maple maybe) by making a template that was much larger but when you traced it with the router made just the size to fit inside the armboard recess with 1/32" clearance on all sides. If you already have one, get a forstner bit the size of the cutout your Rega needs and either use a drill press (preferably) or a good drill with a level on it to enlarge the arm hole. Or you could take a tough piece of sandpaper wrapped around a smaller than hole size dowel rod and slowly sand the hole to the preferred size. Takes time but you can do this with total accuracy.
