Zimo Sound Decoder for Kato ICE4

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Has anyone installed the Zimo sound decoder into the Kato ICE4?  Just got the set (1xMX605 and 2xMX605SL) from DM Toys.  Zimo has the installation instruction, but it doesn't mention where to place the speaker and where to hardwire the speaker wires into the board.  For those who have done it, which specific speaker did you use, and where did you place the speaker?  Any pointers before I start this install is much appreciated.