Hygroscopic BP residue would be my biggest concern, not lift forces. You can always try to preserve them. They're cheap enough to discard every once in a while though. The water glass and calcium chloride treatment would be a quick way to start. Pyrocreations does sell little pre-made 1" cardboard mortars if you're interested. http://www.pyrocreat...tar-1-inch.html They look to just be their normal 1" x 4" tubes stuck onto a base.
For a more permanent mortar, you could look into HDPE. This size of HDPE is often only available on a roll, but sticks might be available. The rolls can also be straightened in short lengths by inserting a dowel into them and allowing them to relax back straight. I've heard putting them in the sun can help. There used to be some places that sold smaller ones like 1" or 1.2", but I am unable to find any in stock at the moment. Pyrodirect has 1.2" and 1.5" listed, but out of stock. Platte River Fireworks has 1.5" and looks to be in stock, but nothing smaller. It also never hurts to e-mail and ask about smaller sizes. It may be available, but just not common enough to warrant keeping in stock.