Best ikelite port to Sigma 17-70?

Hi,

Does anyone know what ikelite port body is best to use with the Sigma 17-70 Macro (non HSM)? Is it the 5510.24 or the 5510.28?

The .24 is listed on the Ike site for Nikon/Canon and Sony - and I use it with my camera.

http://www.ikelite.com/web_pages/2port_nikon.html#seedown

Yes, I know that you can use that one but I've heard that you get some edge softness with it. Have you noticed that?

The .28 should produce sharper images but instead produce some vignetting at the wider end. And now I'm wondering which one I should choose.

Can't say I've noticed, but my DSLR is fairly new and most of the time it's got a macro fitted.

I do use a +2 diopter, as reccomended by Ike to improve corner sharpness.