You might find you don't want to cover the spare or the tanks anyway. Depending on how it's all arranged and how much "slack" you have, you can end up with areas that will tend to collect snow (at least in my neck of the woods). Because of that, I haven't covered either the spare or the tanks. I guess you could put some planks or something under to keep from creating places to hold the snow, but I haven't gotten to that point yet.
1988 Coleman Sequoia - popup (1987-2007)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10