The trick with tambourines is that whatever you mount them to, you will be playing the tambourine as well every time you hit it. So I mount mine separately from everything else, in the base of a basic snare stand, using an old cymbal tilter. This separates it from everything else on the kit, and was made from spare parts.
You can use an old cymbal stand, or, if you haven't got much equipment or space and you really need to mount it, put it on your hi-hat rod for now.
The trick with tambourines is that whatever you mount them to, you will be playing the tambourine as well every time you hit it.
OP, I mean to say that if you want the tambourine sound isolated as much as possible, don't mount it on something you hit all the time, such as a hi-hat stand, on the same rod with a cowbell, etc.
Reverse cowgirl...ha!
In no way do I disagree with your statement, in fact, I agree wholeheartedly......the only real way to avoid spill is to isolate the thing. But I believe it's effect is minimal in a band context.
The absolute best recording method is to overdub, I agree. Complete isolation!