I cannot find a way to keep the old value, except keeping the userdef->obcenter_dia too.
Remove obcenter_dia from ED_view3d_draw_depth.
I have no idea why so many _pad in the two structs. Tried to keep the change simple.
It is been a while. I don't know if this patch fall under the radar, postponed for 2.81 or just didn't get to it yet. Just poking to make sure you didn't missed it.
@William Reynish (billreynish) I put only you as a reviewer, to check it first, before code review. Should have added campbellbarton and Brecht from the start?