Good suggestions regarding the weights, I will pass it on. And I think the feedback on risers making your booth less wheel chair friendly is a good one, too.
Yes, if it weren't paying off I would not be doing it.
As I said before, there is a waiting list to get into these markets. I'm even doing fairly well "in the summer in Florida." There are over 100 participating vendors and we aren't jammed up against each other, which allows the sides of most tents to be visible. The side signs allow repeat customers to find you easily. I like that 3 sides are visible to the public, it gives me more display area. I have garnered a permanent space and I am happy to comply. I am next to a vegetable tent where people stand in line to check out and can see one side of my booth as a captive audience. Many head right over.
Compliance means I don't have to deal with less than professional neighbors and I don't feel that I give up any artistic freedom in my display.