Is more overlap always better?
More overlap can help continuity, but poor electrical contact can still make a wide seam ineffective.
What is more important than overlap alone?
Continuous conductive contact and control of gaps along the seam.
How should overlap be verified?
Prototype the actual seam construction and test it at the frequencies that matter.
Project note: Use supplier data as a starting point. Validate the finished assembly at the relevant frequencies and environmental conditions.