I've just finished my first Bass, CptanPanic, and I decided quite early on to go with two carbon fibre rods (not tubes, but I should have!) to keep the neck stable. I'm anticipating doing a bit of travelling with the instrument, so aiding the warping issue brought me to that idea.
That said, the neck is made of Maple and Padauk, so it's not as strong as your Mahogany! At a guess from what I've seen on these forums, with a 5 string you probably wouldn't need to use carbon fibre.
However, if it interests you as much as it did for me, then go for it!
