Here is my Homemade feeder made from a jello mold. (http://www.imagestation.com/picture/sraid189/p75532af60ed4958e4bcde664cfca5350/f20b11a6.jpg)
It holds about a quart.
(http://www.imagestation.com/picture/sraid189/p8dcbac5ea7b3be5333328a42712de443/f20b1173.jpg)
Here it is without the cover. Let me know what you guys think.
I'd minimize the space between the mold and the bowl as much as possible. The Rapid Feeder, which I assume this is loosely modeled off of, has only room for one bee to crawl down to the syrup all the way around. In other words 1/4" space between the "cup" and the center riser. There is no reason you can't make the center piece any size you want out of hardware cloth.