Best route to Fort Wilderness

The name of the site on the App store for Apples is "Fort Wilderness Sites" It is free, so I may give it a try. We prefer loops 400 to 900 when we take our 5th wheel, which is most of the time. 100 to 300 are OK with the truck camper, with the narrow roads and restricted backing room on many of the sites. However you can't reserve a specific site or loop, as all loops are not open all the time. You can request a specific loop at check in and that does seem to help. They run the campground the same way as they do the different classes of hotels. All appears to be based upon historical data of crowds at the Parks.