The "metal" panels are so light that they are probably even lighter than the 1/64 ply that you ends up using, particularly once you add in the weight of all the paint and other finishing needed to make the ply look like metal. And really for the most part, making aluminum panels out of 0.3mm sheet is dead easy.

And there's just no avoiding the added lead up front with models of these sorts of short-nosed aircraft. I have 800g of lead just behind the dummy on my 1/6 scale Snipe! All you can really do is build the entire model as light as possible KNOWING that you'd going to have to add a lot of lead as part of the normal flying weight of the model.