Well, lets have a look at a few standard practises for these kind of obscenely difficult venues.
Casting is the easy part if it is done correctly. Firstly I would make a cast to my chosen spot by making a mark on the ground in front of me, solely as a standing position. Remove any baited rig and leave just the lead on the line. Cast as tight as possible to your chosen spot if it is shy of the mark by 3 feet pull off 2 feet and use the line clip on the reel to now mark your spot. Re-cast to your mark and see how much tighter this cast is. Continue this process untill you get the exact position. Remember that adding your rig and a PVA bag will stretch a mono line so it's worth taking maybe 1-2 feet off the cast length to allow for this. Also remember to remove the clip after casting. You can keep this mark by now tying on some floss around the first rod ring.