Sorry I didn't provide a lot of detail on the route. It's 108 miles yes - not normally an issue at all for me or the small group I regularly ride with. But there are a few factors making it a bit more challenging.
1 - it's got 10,100 feet of climbing. 2 - a LOT of the course is on dirt roads, a few of them are essentially double track forest roads - seasonal use roads that are closed in winter. That's part of why we end up having resupply issues. Between those areas is a lot of farmland with the occasional crossroad. 3 - because of the nature of the ride we will be out there quite a while...definitely more than a quick flattish century on decent paved roads.
There will be cell coverage about half the route by my guesstimate. I haven't been everywhere along the route but I've been over a lot of it on hikes, skiing, in a car, or riding.
I think I'd prefer the hydration pack route, plus water bottles and a frame bag. Then have SAG on standby just in case. There will be places where we COULD diverge from the route if we needed something - it would cost us maybe 4 miles and at 5 or 600 feet of additional climb to divert then get back on route.