After a not too in-depth look, I've found a few front (not interested in rear bars) sway bar specs (please correct if anything is wrong or add any bars that I'm missing):

Stock: 27.0mm
Mazdaspeed: 27.2mm
Racing Beat: 32.0mm
Tanabe: 30.4mm

Does anyone know the answers to the following questions?

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TIA!

 

I have never seen a tubular sway bar. The only ones I know of are solid bars. As far as adjustable bars, Rick Shaw is the only one I have seen to have a adjustable front bar. They offer a adjustable front and rear. They have 3 different positions/holes for adjustibility. This is the combonation I will be buying when I start my mods. There is another company that offers an adustable rear bar. I don't remember who it was at this time. My 1st gen RX7 had a sliding adjustable rear bar by Suspension Techniques.

 

Both of the stock front and rear sway bars on the RX-8 are hollow. Racing Beat's site has the specifics.
http://www.racingbeat.com/FRmazda4.htm

 

note: you can calulate the rate of a hollow bar by first calculating the rate of the bar if it was solid, and subtracting the rate of a bar that is the diameter of the hole.

since the stiffness is related to the fourth power of the radius, hollow bars are a very effective way of reducing weight while increasing the stiffness of the car.

the other point this makes is that if the bar is hollow, you can tell nothing about the rate from just the outside diameter.

james