I've been lucky enough to re-acquire a 90s Premier Genista kit that I let go of last year. And with them being close to vintage age by now, I was wondering if there are any suggestions of what I could use on the interior of the shells more as protection than any kind of sound enhancement. These shells already are the best sounding birch kit I've ever played, so all I really wanna do it make sure they stay in as mint condition as possible.

Any suggestions? Teak oil?