The ADF hatch was formed in the same way as the windows. All the windows and hatch openings had 90 degree corners and it was established that the cracking stemmed from the corner, not just on the wreckage of 'YP, but on the airframe involved in the pressure tests at Farnborough.
Whilst square windows and hatches on pressurised aircraft were not a problem on piston engined airliners, the pressure differential at the altitude the Comet operated at combined with the thin fuselage skin and the various methods of fixings used were a lethal combination which had neither been appreciated nor tested for in depth in the development of the type.
The Caravelle, as stated above, had triangular windows with rounded corners an th DC10's windows certainly were not square but were rectangular with rounded corners.