Our best recommendation for your application would be our Craft Show Package
. This kit includes a set of weight bags to anchor your canopy when stakes cannot be used. The weight bags can be filled with sand, gravel or any similar material. Please keep in mind that in very windy conditions it is always recommended to strike your tent to prevent any damage.
To your question on flat-top canopies, we actually have never sold any of that type of shelter and cannot speak to their efficacy.