Heavy duty plastic tub, lined with scrunched up newspaper and a plywood (8-10mm )lid cable tied on at 50 mm centres,use heavy ties. Alloy v8 speedway motors are shipped around in purpose built plastic tubs and lid. I have felt a 410 ci motor raced in at Kwinana WA on a Friday night,pulled out,packed and flown in a tub to Melbourne,arrive Saturday morning, and then to Warnambool Saturday arvo,it was still retaining the heat from the night before.!!!