I'll be riding but starting at 7 for the 100m so will miss you at the start. I can't see a problem. I did the metric last year, my first, started at 7:30 and we took our time, a few longer breaks, got in a bit after 1 and there were still lots of folks trickling in. Also the slower 100milers of which I will likely be tomorrow trickle in all afternoon so you should be fine. They're still saying maybe 20% chance of rain, tapering after 10am so looks like a go. Have a great ride!