Run/ walk is 100% possible for a Bill R. I did it last year. My strategy was run ~10km between walking breaks. With a lot more walking at the back end. When I was running it was at slightly quicker than sub 4 hr marathon pace.
I'm also nervous about the down, completely underestimated the downhill running in 2014, the quads had been pulverized a long way before the end.
John - i ran an 8.30 last year for my first Bill R. My run walk was 9km run 2 min walk. With a bit more walking in the final 20km.
Lowrez & Dannirr - scrolling back i've seen the chat about some awesome sounding patches and tattoos. I imagine i've missed the boat, on the off chance i haven't would love to get involved, let me know cost etc.