[PSUBS-MAILIST] hemi vs elliptical

[hank pronk via Personal_Submersibles]

I wonder witch one is stronger to mount a bow dome into.  My guess would be an elliptical if the entire radius of the knuckle was kept in tact or at least the bulk of the radius.  I notice in a drawing of a Perry front head and dome that the reinforcing and mounting ring are very light compared to what we see today.  Is that because rules have changed or is it because the dome is mounter into a hemi?  
Hank