The GI7-BT mod is the way to go in the absence of good 572Bs. But the thought occurred to me that it might be a lot of fun to replace the 572Bs in my SB-200 with a pair of 813s. It looks like they might fit. But I doubt that I'll do that. Besides, I don't have either the 813s or the sockets. 73, Mike www.w0btu.com