Advice on using 17-70mm Sigma dome port for NEXUS

I am looking at trying the sigma 17-70mm lens for my nexus D200 setup as people have had good results with this lens. However Nexus to not make a port for this combination at the moment.

I have a 12-24mm nexus port and also the FP160mm nexus port comming.

I am trying to find out if i could possibly use one of these with an extension piece.

Any thoughts, advice appreciated ??

On my Subal with a Canon 20D I use the Sigma 17-70 with the same dome/extension as I use for my Tokina 12-24. I'm more than happy with the results.