I'm not committed to any particular leather, as long as it will hold up against salt water and other abuse reasonably well. Could be CXL, or shell, or that Horween "Essex" leather.
As to wiggle room, it's a little of everything. Actually, now that I sit in the 12Es, they seem to be accommodating me on that front. And I was starting to worry about lack of support from the 12EE. But I am willing to listen to those with more experience with this problem.