I'm not so sure Chimo. Although there is a lot of splashing going on, the AV plate seems to be well above the water - looking at it on the phone at least.
kc, can you trim the motor so the AV plate is parallel to the keel, then use a straight edge off the keel and measure up to the plate (and take a pic)? This will be a good 'guide' of where you are currently at.
Also, what shape is the very bottom of the boat/keel? A vee, or some sort of keel shape (from the rotomold) that provides extra protection to the hull? Pic of this from behind too would help too.
Cheers
PS. From what I recall of reading G2 300 threads over the last 6 months or so, they referred to 3 different prop types being used. RX4, REV 4, and a Bravo 'something' (can't recall if a 3 or 4 bld.
Can your mechanic get hold of a REV 4 17" or a 19 to try Kev? 19 maybe too big though I think. These work great at high mounting positions.