sort of figured that there must be a reason that the manufacturers are not doing it this way. Thanks guys for the response.

Any other odd ball solutions like using the tube as a mould for a number of layers of carbon fibre but leaving the ali tube insitu, would you get such uneven stresses between the carbon and ali tube that the epoxy bond between the two would shear ? <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />