I'd like to buy an ebay Stofen type diffuser copy for my Minolta 4000 AF flash. I need to find one of approx the right size. Could anyone tell me please the dimensions of the flash head (where the diffuser pushes on) on their SB800 and 580ex as these are the types of flashes the larger diffusers are advertised for? The Minolta is pretty large at 80mm x 52mm so I guess these might be close.