I'm not sure why you'd want to use montueka in a bopils, but magnum is a pretty standard bittering hop. I don't think I'd waste the spalt as a bittering hop if you're using montueka as a flavor/aroma hop. If you're using montueka, the "style" is thrown out the window, so I wouldn't worry about using other hops that are "to style."
To paraphrase Dr. England - "Off-flavors smooth with time. So do mountains. Brew it right from the start!"
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