Update: I've reached out to everyone I can think of and nobody knows of a FiST with a Mountune rad and a Mishimoto/Whoosh cold-side pipe while a number have said that they tried and gave up.
I've asked about the cp-e cold-side with a similar response: nobody can say, for sure, that it'll fit.
So I guess that I'm selling the Whoosh pipe and tapping the stock pipe.