Voyd the Voyd - help

Hi
I've got a voyd the voyd 3 motors, it plays greats but needs some service.At present the top plate is not fixed in no way to the wood base but it seems to me that it was fixed by some glue. How is correct to fix the the top plate to the wood base ?
Likewise other TTs the top plate sags just a bit in the centre, as a result of that the motors pulley axis are not strictly vertical, notwithstanding that when the tt. playing the belt doesn't slip out but run a bit higher the pulley middle centre. To get the best from the TT has the belt to run strictly in the centre ?
The 3 main springs have over 10 years but seems to works perfectly, is it better to replace them ?