Depends on several factors:
single or dual tower drive, size of decoder and speaker.
you might mount a decoder vertically in one end, the speaker in the other end where the fan openings are.
you do need care not to place the decoder too close to the plastic body, (at least the heat sink side).
you can also perforate the bottom of the fuel tank to locate speaker there. Unless you plan to fill it with weight
the late Joe G, former publisher of OST, wrote a blog article on decoding that engine. It’s online.
