40D, Ikelite housing but zoom clamp / gear sleeve problem

[Mucksavage]

I have a 40D with Ikelite housing. I am trying to set it up with a Sigma 17 - 70 lens. I have both zoom clamp / gear sleeves that come with all housings. Both zoom clamps are much bigger then the lens so to make them take I need to use the thick rubber underneath them - but then the diameter is far to wide to slip on the gear sleeve.

I think 40Ds, Ikelites and Sigma's 17 - 70 lens must be a common combo out there SO CAN SOMEONE PLEASE EXPLAIN THIS TO ME!??!

Thanks for your patience.