Help with cougar cub modifying

Sorry about large pics im going to have to start scaling them down on my phone.

Anyway what i have planed is to build up the transom 5 inches higher to accept a 20 and at the same time im going to make the sponson part of the transom full hight which should strengthen it alot.
Im also going to add 2 large knees.
My question would be how to tie these into the hull as there is no stringers or core in my little cougar.

Will post pics when i get in the boat next.

 

So transoms out and rear skin is delaminated. So ive started grinding the delaminated skin out and the hull for bonding when i tab in the transom to find what looks like a foam core??? Aprox 2mm thick wtf :$