I think that Markpoint Z is way better fot that situation, because it saves the position automaticly.
I might find good to use HUD SOI TMS aft only when i want to point my TGP directly in front of me, and this is rather rare scenario, because I'm so used to HMCS functionality (DMS right long), that works also in front of you with proper HMCS settings.
EDIT: After some tryouts I found this mode pretty cool with LD bombs in CCIP mode with combination od HMCS SPI always visible settings. That will make you always see where your bomb will impact event throu instruments.
Of course you need to have your target marked by markpoint/waypoint to see it. And this will allow you to make your dive shallow and drop bombs exacly where it should be with CCIP whitout limitation of poor HUD point of view.