lancaster FN5 turret cupola

Hi , i am trying to construct a Lancaster FN5 front turret cupola and the accommodation plate , this is the base that the cupola sits on.

Has any body got spare an interior roof cast  frame  , it does`nt matter if its cracked or has some of the lugs missing as all this can be repaired ?

Also does any body know what the measurement is from the inside edge of the accommodation plate  to the outside edge at the front of the plate ?

I am using a wellington accommodation plate as per picture to mark out the inside edge , hopefully they are the same and i can position it in the correct place ?