I did acoustic foam on the back, cotton, felt. Also some duct seal on the driver and micropore on the vents.

Cool, thank you for the response. I have settled on a specific fill. Going to listen to that for a week or so then try something else and see what I notice. Thanks for all the great info you have wrote up about these.

Any chance of over stuffing causing the bass to be boomy?  It sounds less boomy with less cotton in it. But if I stuff it so much that there may be some pressure against the back of the driver it becomes boomy.   Pretty new to listening to specific things and seeing how different mods sound. ...