Gidday Mo, have just rebuilt my motor from the ground up and used composite gaskets for both head and barrels and no problems at all.I did however make sure the head was re-torqued at 50,250 and 500 km (apologies to those of you who are metricly challenged).I have always used the composite gasket for the barrels and have never had leaks from 3 different rebuilds.Although you can't really torque the barrels unless you have some fantastic special tool that I don't, you do need to tighten the nuts following a rebuild and make sure you use flat washers under the nuts.Was the head gasket replaced because of piston or ring failure if so were the carbies given a good clean?Good luck mate keep at it!