knowing the added weight doesn't mean you know where it is...
Run a thinner than spar ID rod from each end to find each end point - simple.
Then, given it's overall length and the ID of the spar combined with the mass, means you can work out its density and have an educated guess as to what the material is. Which brings me to....
Our black TL has 14g of lead......
I
really hope that you're using "lead" as a stand in for "unknown, high density metal or metal alloy" 'cos lead is not to be messed with. Anyone
selling a product with lead in it is asking for a world of trouble too.
Meanwhile.... that is a hell of a lot of weight for any kite but on a
Light 
Hey, if it works for you....
Mike.