I'm hoping some veterans can help me figure out what kind of pace to shoot for in my first PPM coming up. My fitness is that I run a marathon every month or so, recent best time (Boston) 2:56, I do about 60 miles a week, most of that on medium-rough trail, with one 8-10 mile steady-state run @ 6:30ish pace and one 6-10 mile uphill treadmill slog at 15% at a 12 min per mile pace. (Hell day) I run trails quite a bit in rural Virginia, so I get a lot of downhill work too. I did the Zermatt ultra last year in 5:45, but that course tops off at about 10,300 feet. I was coming off an injury and not pushing it too hard. On the other hand, it's got very little downhill to go with the 8,000 or so feet of ascent, and the steepest parts are at the end. I guess the wildcards are trail and altitude. My friends who've hiked the trail tell me it's not too technical but gets rocky up top. I live at sea level but will have a couple months worth of breathing 21,000 foot altitude-machine air for 45 min to 1.5 hours per day, which seemed to help me cope with the lower altitude in the Alps last year. Is it impossible to really pick a pace with this many unknowns, and I just figure it out along the way? Just pick a sustainable heart rate and work off that? (my method for unknown trails races around here where GPS is going to be too far off to use). I'd love any advice.