Lobo1,
At the risk of being redundant here is a clarification with your picture altered.
My apologies if I got the wrong impression, but if you measured the height of your cavitation plates relative to the height of the bottom of your keel, you need to revisit that - I believe the base of measurement (where the straight edge lies)needs to be where the hull and transom meet directly fore of each motor.
Bushwacker's measurement is taken at the keel because that is where the engine is inline with the bottom of the hull (because he's running a single)
For twins set up the strait edge needs to rest on the bottom of the hull approximately where the white squares are in the picture.
