thanks for your interest dan , im not producing them commercially ,just had a large piece of aircraft alloy lying round in the workshop and i was also struggling to get towers that would last longer than one outing , also i noticed i was splitting bodyshells at the midway point where in a contact the chassis was bending/flexing so much the shells were splitting , so the battery strap stiffned it right up and cured that problem , it also works as a great heatsink , sorry dan but thanks again