Titanium (22) is almost twice as heavy as Aluminum (13).. But it does have some properties that make it interesting but to go lighter than carbon you looking at lighter elements. Carbon is 6 so that means the elements lithium (3), Beryllium (4) and Boron (5)..

I'm not an structural engineer or materials scientist.
One could investigate a carbon/boron beam.. Increased modulus but like everything its a trade off.. As modulus goes up so does cost and so does its brittleness.. So its benefit may not be great even in a fully "open" class. You would just have to add more lead in the F16!!

magnesium aluminum alloy beams I suspect would be close to or above a carbon beam in cost and I shudder to think what a lithium-beryllium based alloy would set one back..