I don't and see no reason for it.
The inside (unless you store your yak outside right side up with no cover -- spell that rain / bird poop catcher), the inside is not going to see much sunlight.
Waxing also make it slippery when wet. In fact I did not completely fill the cloth to keep it rough -- grippy.
Good luck.

: Hi everyone,

: Is it necessary to varnish the inside? I saw it in Tom Moore's book, but I
: don't think that I've seen a reference in Nick's book or in Joe's
: instructions. I tend to use a cockpit cover when I don't use the kayak.

: I don't like the idea of sanding the inside since I would end up in the cloth
: which I think is worse.

: The commercial yaks don't have varnish either on the inside.

: Any advice is welcome.

: Andreas