[RWebb]

BEST: Heat it or use a dehumidifier

2nd Best: Use a fan and insulate it to reduce temp. swings at night

ALSO: do NOT use a car "bag' (unless it is one with a fan) that will trap humidity in the enclosed space.

Spray LPS, Boeing T-9 (?) Tectyl or similar over every surface.

Expect the leather to get moldy and fabrics to rot...

Sure you can't put it anywhere else?

Also, keep it as far as possible from the ocean, from ocean winds and salt spray.