Jack plate

[Nasher]

Hello all

My RIB's Transom is built to take a long shaft (21 inch) outboard, however I've picked up very cheap a 200HP Suzuki EFI thats unfortunately an Ultra long (25 inch) shaft.

I'm thinking of making a fixed or manualy adjustable Jack plate with minimal setback rather than trying to build up the Transom.

What thickness aluminium plate should I be using, bearing in mind I'll be putting 200HP through it and wave jumping a 24 foot RIB.
I have some 20mm plate in my garage that looks about right, however I'm tempted to try and find some slightly thicker.

Thanks

Nasher