Transom Height for 15 inch motor

[Ametuer]

Hi guys i have a chaudron 22 (phantom21) and while doing the transom i am transitioning to a 15 inch 3.0 motor and was looking for transom height suggestions. Also when using the 2.5 280 swivel bracket does anyone have any photos of were they cut ? Thanks in advance.

[RossM]

I went with 550mm which results in around 57mm below.