If I can enter the argument as a very long time serving Canberra PR9 man, the PR7 prototype in the photographs have the PR9 wing root cord extension but not the square PR9 wing tip extension.
The PR9 tip tanks fit at the original B2 / B6 mounting point and are identical to all other Canberra wing tip tanks.
Although many were modified to fit chaff dispensers/ radar heads and other bits of trial equipment all remain the same three point mounting with explosive bolts. The PR9 wing tip extension, which is not readily removable, is not primary structure and is supported by an extended internal spar which will not carry the weight of a full drop tank.
Last edited by scorpion63; 23rd Jul 2013 at 11:54.