Well, from the pictures we can't tell the condition, style or depth of your neck mortises, or what the existing overstand is on each bass.
So what can i postulate?
- the Gilkes has a full length heel with little upper rib taper. Increasing the overstand from 30mm to 40mm would decrease the gluing surface by 5% and increase the leverage on the joint by a similar factor.
- the Hart has a very short heel. Increasing the overstand from 30mm to 40mm would decrease the gluing surface by nearly 8% and increase the leverage on the joint by a similar factor.
- the Storioni has only slightly more heel length than the Hart, but the mortise looks fairly shallow compared to the others, and the button appears just tacked on, so that 7-8% may be more significant.
- the Olde English has what looks like a dovetail mortise. That would change things again, if resetting the overstand was possible using the original dovetail, ie: not converting to an italian heel.
I would hesitate to make any generalisations, however I think a good luthier would naturally compensate for any changes in geometry (overstand or angle), and the reset, if done well, would not compromise the strength of the joint.
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