Can outdoor-rated 3/8 inch porcelain flooring tile be installed without a cement or concrete base? I have a 12'x12' area that has 4 inches of compacted 1/4 minus. The tiles are 9.75'x9.75', 3/8 inch. I've read a handful of articles that refer to sand/gravel bases, but they are typically referencing 10mm tile. I'd prefer not to have to lay a cement/concrete base. Thanks!