If you cut large holes in the tail area, consider:
--You will need ribs or truss structure to support any external skins. They need to be sized to handle buckling loads (compression induced bowing) Gluing to the overlying skins prevents buckling until the glue line fails or the wood crushes. Thinner and harder internal struts might be considered better if well glued to the skins
--If you choose to leave out the wood skins, then be aware that the covering is now supplying much of the stiffness. Or, the stiffness removed is not actually replaced if the modulus of the finished covering is poor. However, I've seen some pretty "holy airplanes" that performed way better than I expected them too. Around here, Tim Meeks was a proponent of this kind on construction, I believe.
--If you leave out the wood skins, also be aware that people handling your plane will have to be advised, repeatedly, where they can hold it. Or you will get holes. An after the fact, unintended holy airplane. Trust me on this one....
--Orienting balsa skins with the grain pure fore/aft direction may improve the lateral stiffness and help avoid tail whip, but it is not as good in torsion. If your plane handles corners funny, ask someone to watch from behind as you pull out of a square corner. Does it have pronounced stab tilt? How much is it interfering with your trim? If memory serves, when you twist the fuse you will get some max stress aligned at 45 degrees to the longitudinal axis. (Balsa is a non-isotropic material. Stronger and stiffer along the grain. In composites, they layer uni materials to take advantage of that. You can also do it with wood. That's why plywood is so versatile.)
--The best way to figure out a building style is to keep weighing everything and keep records. Build it one way, but compare what you likely would have gotten the other way. I've done some studies like this and as Keith pointed out, you can get pretty fancy and not save much. Worse, you can get fooled into using more zoot, like carbon fiber pushrods and such when they are not needed and simply get heavier. Weight is a touchy subject, especially during the design of full scale aircraft where careers are at stake. Just ask any Mass Props guy....
The Divot