I believe there was a thread about these..and I saw a guy who modified his to made his with 2 small holes in it by drilling it for the hot water to fill up..but he had the thicker walled ones...anyways tell us how they worked for ya!
I've tested the bowl out just now, it's quite nice for my ej medium brush. Any bigger and you would need the next size up. These things also conduct heat like mad! Hot lather is no problem with this.
It is a tad light in weight but for £1 it's a bargain.