Highly unlikely for the Stirling. Its bomb bay was long (42ft) and shallow but divided longitudinally into 3 by heavy beams, leaving channels only 19 inches wide. They managed to squeeze in mines which were about 17 inches wide but an 18 inch torpedo is probably a step too far. It certainly wouldn't accommodate the torpedo MAT fitting used later in the war to aid dropping at higher speeds and altitudes without modification of the bomb bay doors, something that had to happen with both Hampden and Wellington when they became torpedo droppers.Also, although the Air Ministry dropped the torpedo carrying requirement for the heavy bombers, any of the big 3 could have been easily modified to carry a couple of torpedoes internally.