Although caution. If working IFR traffic we would normally not descend below 500ft above base of CAS, however it is not unheard of to give a pilot on a visual approach not below a level which is the base. I don't do it personally but I know plenty of people who do. If I were you, I would check in with the controlling agency if planning on flying at the base of CAS. Lets face it, it is not in your interest or mine if you meet a B777 coming the other way!