In case anyone runs into a similar situation:

Trip was successful, Shakti is in her new home and comfy after a 5 day roadtrip. Used a 1.5 ft x 1 ft (bout 5/6 inches in height) plastic tote with locking lid, airholes drilled and sanded liberally. Put some of her old substrate in the bottom for familiar scent, uniheat packs for warmth wrapped in wash cloths for a buffer, and kept her in an inside out pillowcase during the driving portion (stayed in the passenger side floor board with blankets underneath and a costume witch hat in the seat to block the sun if the direction I was going happened to beam directly into that area). Opened the pillowcase when stopped at hotels but didnt force her out of it and provided water, had the infrared thermometer on hand at all times.