I acquired a Jagdpanther not too long ago with metal tracks, sprockets, idlers and gearbox and the thing weighs a tonne compared to my other tanks. I love my Sherman, but it is way too light in comparison. How would I go about adding weight?

I was thinking of adding metal sheet to the inside of the lower hull and covering the metal sheets with Styrene to prevent shorting of boards and what not. I was thinking about adding weights, but I don't want random bulges of metal lining the inside.

Any thoughts on how this could be achieved without going overboard?