28mm copper plus a swept 90* bend one end & 28mm straight connector on t'other would give 31mm O/D plus if solder fittings used they will have a swaged ring which will prevent the hose pulling off.
sounds ok do you have this ?
Bob the new 32 mm hose i have is thicker than old and a bit tight to bonnet so thinking of getting it away from exhaust in metal as much as pos