Routing a cavity is normally a precision work.Once is cut means is done.So accurate measurement should be considered like the routing guide sleeve also.The cavity should be painted not leaving at raw wooden marks.
Thus,this process esp.the cavity should not be 'exactly' fit.
Freelance basis,got all tools/equipt.2 do all this things.
I start doing this since late 80's
Own a shop???many things hav to pay??
Interested sms me @92988974