I shoot 100% macro and use a 180 on my d300 and af-105-vr with and without a subsee +5 and +10. I have enever had a problem on the bottom or shooting up. In fact, with practice you can back off a couple inches and still see the image. I only dive a couple of trips a year and figured the 45 would forever be a pain.
Actually at the magnification of a +10 Sub See all I can do is get a single focus rectangle on a pigmy. Here is a writeup from yesteryear on the process. A very small pigmy in very low resolution from that presentation is attached. It has been formatted for the presentation but is full frame.
That was 2011. I have increased my technique since then but no interesting pigmys