Until just a few days ago my only bag for the 5x4 was a Tamrac Expedition 8. Big, sturdy, and also from about 15 years ago when I was considerably fitter and stronger! It takes practically everything, my Shen Hao, 4 lenses (90, 160, 210 and 305), 6 DDS', a 6x12 roll film back, 120 film, light meter, loupe, Lee filters/holders/adaptors, and at a push a Polaroid 545 plus quickload film. And the usual sundries like the dark cloth, lens cloths, cable releases etc.
However the camera has barely moved in the last couple of years as I've been unwell for a good while so all that fitness and strength has long since left the building, so lugging this monster to the end of the driveway was more than enough! I was looking for an alternate bag for my digital gear and ended up getting another Tamrac, this time an Evolution 9 (5789) for a mere £17 delivered. This gives me better and more organised storage for the digital stuff, but importantly it also allows a quick swap over to a basic 5x4 setup without faffing about and changing dividers etc, and it's just over 1kg lighter than the Expedituon 8. I just take out the digital lenses, put in 2 of the LF lenses, the loupe, light meter and the 5x4 (which just fits in the top compartment and means there's a real chance I'll be able to take the 5x4 for a wander from my front door without needing an ambulance at some point. In theory, I've yet to put all this waffle into practise...