: Anyone know of an elegant solution to sanding the inside of the
: hull?

: Marc

Not elegant, but I've used:
a) A cheap 'disk adapter' for an electric drill (these use the discs with the hole/star in the center; I don't know if they are even available any more...). One key is to use enough pressure to bend the (soft) rubber disk to the hull shape and avoid letting the edge of the disk cut.
b)For hand sanding, I found a soft adapter pad for my ROS in my tool collection. It wouldn't stay stuck to the random orbital sander any more, but it would grip a hook-and-loop sanding disk. With a 40 or 60-grit disk, even hand sanding can go quite quickly on cedar.
c) A cheap (not carbide) 'paint scraper' can be reshaped to a curve on the grinder, and is good for getting rid of glue drips and rough spots inside the hull.

As has been mentioned this is more of an issue with a canoe (where all of the interior is visible). With a kayak, I'm only 'particular' about the high visibility areas, and on occasion have used filler to smooth up the ends before glassing the inside.