pwfletcher,
GREAT set-up.... let us know how it works out for you!
You've got the Custom Flat Port as well as the Macro Port set-up for your new 105mm...
To go wide angle, you'll need another type of port... Sea&Sea currently makes two wide angle (a little about the third port, later) ports; the NX Compact Dome Port and the NX Fisheye Dome Port. Both ports work well, however the larger fisheye port would give less-to-no image aberration, and would allow for wider angle lenses.
The need for wider wide-angle will be of some concern to you because of the 1.5x crop factor of your D100. Therefore, what works well for my N80 (i.e 20mm) may not fit your needs (the Nikkor 20mm would be a 30mm on your D100).
If you are just starting out in SLR housed underwater systems, I would suggest running macro until you're proficient with all of the the camera and housing's capabilities.
In the very near future Nikon is coming out with a 12-24mm ultra-wide lens (that would correspond to an 18-35mm lens on a standard 35mm camera) made specially for the Nikon D1/D100 DSLR's. When this new ultra-wide lens comes out, I would call those guys at Underwater Photo-Tech in New Hampshire to see if they can manufacture special zoom gears and purchase the appropriate ports at that time.
If you HAVE TO shoot wide right now, I would suggest trying to find a new (but discontinued) NX Standard Dome Port and mate it to the Nikkor 20mm 2.8D wide angle prime lens. This set-up works very well for me - and is the least expensive way into U/W wide angle photography. The Nikkor 20mm 2.8D lens on my N80 is similar in focal length to the legendary Nikonos 15mm, and shoots superbly.
--Brad
