Coosa
 

I noticed you asked about coosa board. Here's my take

Good: strong, water impervious to a point, lighter than ply wood.......

Bad: expensive, hard to cut ( will dull blades fast ).......

Probably much more to be said but that's it in a nut shell.

Ed

Penski Board is an option. I did my 20's transom from the outside with it (2006) and it has been fine so far. Don't know what materials cost now, but the Penski Board was not cheap.

I used Coosa for several reasons:
Light weight (26lbs/ft3)
strong with very high compression strength
won't rot
won't absorb ANY water
cuts and sands easily (almost too easily)

Like everything else, it has a few negatives:
is not great at holding screws without a bedding of some sort (through bolting is fine though)
low/no residual strength if it ever fails (ruptures rather than plastic/elastic failure)
dust from cutting is extremely itchy and dulls blades fast - just like FG
need to make sure that it is fully wrapped in layup since exposed edges can be failure source since it is so friable (the front and back surfaces have glass embedded about 1/16" deep)

oh yeah - I got it cheap due to a mis-quote :D

Yes. :(

Thanks guys for the input I’m looking at a full stern rebuild and only want to do it once ... any thoughts on a full stern with brAcket vs the traditional motor well design I like the security of the solid stern and understanding there is a cg issue but I’m most likely gonna repoower so I can make the needed adjustments when i rebuild ... just not sure the best way to go

Estimating CG Shift
 

In doing your homework you may want to see my post of 9-24-16 on Estimating CG Shifts. There is an example calculation which you can plug in your own numbers. You may also temporarily load some weights to simulate your final config before spending time and money. Lots of guys choose brackets for similar reasons. This gives you a chance to consider the effects. Best wishes!