I probably have a few more options yet to get it really hot (taller candle, oil lamp of some sort, etc) but I don't think it should be this hard to get this thing to work (based on the reviews)
However... If the grid were down, and all I had were some candles, I think maybe I would still rather have the heat go into these things to be kept low, instead of the heat of a candle ( no matter how small ) go right up to the ceiling.
The theory is nice to have in my brain just in case I have some extra flower pots and fasteners available in the yard to maximize the energy. I sure as heck would not buy it for a pre '65 dime for it though.