@Mike: Have a look at this older thread, there are lots of ideas there of different solutions people have found. Start at page 8 and work back, as the earlier posts reference gear that isn't available any more.
@Chris: You pic gave me a forehead slap. I've been leaving the camera in the housing, and placing it in cases like you would a DSLR, across a narrow end. But the EM-1 housing is too wide with the handles and I've bene griping about the extra disassembly that meant. It absolutely never occurred to me to put it across the wide end like you have done and use the DSLR compartment for a dome! I'll be trying your arrangement next. Thx!