I have the Saunders LPL 4550XLG/VCCE enlarger which is also a known light leaker. In my opinion there are two kinds of light leaks with this enlarger. The same thinking may apply to yours. There are leaks that also have hot air coming out. These are cooling vents that also leak light. When first trying to address these I unwisely taped them off. In a very short time the light bulb burned out. A new bulb and a spare had to be ordered at some expense of time and money from 500 miles away. After that mistake I tried to direct the light away from the easel using fabricated baffles pointing the light toward the walls or ceiling which as has been mentioned were painted flat black. The other leaks could be taped over with gaffer tape. As you may know the advantage of gaffer tape is that it can later be removed without leaving residue. Hope these ideas help with your situation.

John Powers