"A bit of thread necromancy, but as equipment and not weapons, I believe they should actually weigh 1/4 of the large-sized saddle. Any thoughts?"
As a DM, I'd rule that the saddle weight is based on the mount's size, not the rider's size.
Therefore, the default saddle weight would be for Large mounts. A saddle for a riding dog or a pony would weigh half the listed weight.
Just my $0.02...
