Thanks very much Keefer. Appreciate this

faced with 103db limit at oulton park, and no time to sort things properly, a swift and cheap solution was a couple of tescos scouring steel balls in each pipe - 98 pence! and a couple of bolts to stop them flying out.
ran a tad richer, but saved the trackday......

Bloody hell. What, you push them right inside or just in the spouts?

shoved them in just a bit ( gas pressure wants to blow them right out again) bolts prevented them flying into the face of following riders.....
i've kept them in - it's just taken the edge off the sound enough so i'm not warning the police in Hertfordshire of my arrival, and prevents neighbours getting upset.
i'd be the first to say that i love the sound of open pipes, but i'd like to be able to get away with the riding i do, without getting too much attention from the police. All legit in other respects, but given the choice, wouldn;t you rather carry on riding, rather than be pulled for a spot check?

downside is it feels a bit stifled, but bike really needs a bit more attention anyway (valves, dyno run, possible power commander) Ideally would like db killers, and have two maps for loud & silent running. But that involves time and money which i'm spending on other stuff at the moment.