You can get an idea of the challenge from Doug's photos of a Hornby 08 installation at the end of Gary's review which you can get to via this link.
Installing sound in an 08 has definitely been done as South West Digital sell their own sound recordings in the ESU LokSound decoder. My guess is that the speaker is relatively small and takes up the cab space. Googling for the appropriate keywords might help. There is bound to be some video of a sound fitted 08 on You Tube.
yes it has been done and it is very very quiet in all honesty i dont think it is worth the hassle. if you really want a small engine with a sound chip fitted then go for a 20 it may be bigger but that means you can also get a bigger speaker inside.
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