Share 'Tiki 26 Changing Secifications Aluminum Mast'

Could I get away with using a standard (oval) aluminium  mast section with internal track for the wing sail which has been recommended by Rolly Tasker rigging dept? The specified aluminium tube is not available localy. The  closest I could find was 140mm diameter 4mm wall. Too big? The specs in the plans are for 127 diam 2.5mm thickness. Could I go smaller 101diam ith slightly thicker wall of 3mm…