Fitting sound to Hornby R2881 black 5

[clubman2b]

Anyone fitted the Hornby sound decoder R8114 to a Hornby railroad R 2881 class 5 which is already dcc fitted.
The speaker supplied is large and due to the design of the loco and tender (see Hornby service sheet HSS347B)it is unlikely it could be fitted, even in the tender.
I understand a sugar cube speaker could be used and if so is it possible that it could be fitted in the loco ,preserving the normal disconnection of the tender ?.
Any advice would be most welcomed

[Walkingthedog]

A sugar cube in the loco would be best as the tender has the Ringfield mouding taking up all the room.