I have not owned an extensive quantity nor variety of drums during my life time, (I started playing in 1963 and keep my sets for a long time except in the 80s when I went on a buying spree, and have only owned Rogers and Ludwig), but I have noticed heads fitting tighter than others and even wondered if the heads were the reason.
I really don't know what procedure the factory followed on the shell thickness with reference to pearl or non-pearl finishing. I have read that or understood or interpreted that shells were manufactured first, then inspected to determine if the grain pattern was suitable for staining. Those with proper grain patterns would be candidates for stain finishing and those that weren't were covered. Did each manufacturer establish their own practices?
Towards the end of Rogers existence (80's) they started putting plastic pads under the tension casings, which I thought was specifically due to stained (non-pearl) shells. I'd have to go back to my literature and take a look.
Thank you all for your input, much appreciated