Sorry, I can't help with the dimensions, as I only have a couple of the plastic Cox series. One is the Aircobra and that flies well in calm weather, but get a wind and it balloons into the wind and dives on the downwind leg. It can be alarming and you need your wits about you.
In my limited experience, I have found that planking over formers gives me a lighter model. But that may mean I am lousy at carving! An alternative that might be worth trying is carving blue foam. Some Pistachio models I have seen (including a Spitfire!) have flown extremely well.
Best of luck,
Andrew.