Most important: I've got sandpaper and I'm not affraid to use it.

When you're looking to save weight, remember that every ounce removed from the tail will allow the nose to be a few ounces lighter.

I hardly ever build a balsa sheet tail surface. I usually build a lightweight frame with most of the same thichness and sheet it (saves about half the weight) or build two thin frames and attach those to either side of a thin center sheet which then gets lightening holes (saves 2/3 or sometimes more.)

Pull-pull systems make control more precise AND remove most of the weight of pushrods. And , again, a lot of the pushrod weight is in the tail, so you get a bonus multiplier for all of that part.

The best covering available (in terms of strength and arguably in terms of appearance, thogh definitely not in terms of ease of use) is also the lightest by far... that would be micafilm. Very easy to save a couple of ounces in the tail of a 3-D plane with big tailfeathers.

Wanna get extreme? What are your wing ribs made of? There's an awful lot of strength in a T-section that supports the covering over a well designed center spar (nice warren truss for instance with some extra webbing where needed)... To take a much simpler approach, cutting holes in wing ribs doesn't hurt, but if you add up how much weight it can do away with, it's not the most helpful thing either.