Thanks! Interesting info sharing on the Wed/Thur being good days to arrive, due to departure. Suspect that is variable based upon how far a NP is away from urban areas. For example, Yosemite is 3-4 hours away from many heavily populated areas, that the exodus of weekend warrior visitors takes place on Sunday. I also find that many of the popular fishing lakes/river campgrounds (State, County, COE, NP, Etc.) usually show Fri/Sat reserved, and then open spots during the week.
With Glacier being both a mega draw NP (like Yosemite and Yellowstone), but also a good bit of a drive for those that are one or two week vacation mode - I can see your logic on needing a few days to head back home. As we used to do the same thing, usually leaving Thursdays from popular draw NP's, to allow the travel time and unpacking time to start work on Monday's
We'll see how this works out. If I had known we would be going to the area, i would have made reservations at St Mary on the East side.
I did call and talk to a Ranger, and he also suggested we consider Two Medicine, he said we would fit with our coach. But looking at the NP site, they say max length is 35' (May have been 36'.), so I wonder if he forgot I mentioned we're 40'(?). I'm going to call back again today, and ask for clarification. But being a smaller campground, suspect the odds would again be lowered on finding a site that will hold us. (And not complaining at all, we purposely picked 40-42' when we bought, knowing it would limit out options going out. Not a major problem when we plan properly, and this is a classic example where a change of our travel plans makes this now tight scheduling in peak area of high demand areas