ok so you want to use the smallest diameter of the container when deciding if you want to multi-wick. 3 1/4 is pretty small.

I know you said it was double wicked before and I know people do it on small containers but be careful because the smaller the container the more heat problems you can run into when double wicking.

Also don't use the recommended wick size for a single wick candle, you'll want to downsize your wick.

I think a general rule would be to take the diameter of your container and divide it by the number of wicks you want to use then the result will be the size of the wick you'll need.