Why build an aluminum frame when you can build an Titanium frame. It maybe quite expensive tho but if you are a full freged racer you might be will in to parchuce one. While your makeing the frame out of Titanium why not the a-arms, swingarm axele exc.? How much lighter than a stock DS it would Be? How much lighter than an cromo frame would it be. What grade of steel is the stock frame made from?

 

I think among the commonly known exotic materials, titanium has to be the hardest to work on. I don't know in english, but in french, titanium is actually a composite, with Ti, chromo, and aluminium...pure titanium is too sooft, if I remember well.
Amyways, it costs a whole bunch, and is extremely difficult to weld. I heard countless bikes (from very reputable builders) with snapped frames, mainly at the steering stems.
I'm more a carbon fiber fan...

 

Rad mfg. makes a titanium axle. it cost's 800 dollars but should prove hard to bend or break. They also make an aluminum axle which makes not sense to me. It costs 500 dollars. it may be lighter than stock, but aluminum is not the strong stuff in the world to make axles out of.