Replacing transom, should I beef up inner skin?

[TMala]

https://photos.app.goo.gl/XnmjEs4hFQvQB8Xt8

The photo didn't show up, still trying to figure it out! But hopefully the link works. I think I figured it out, the core that came out is 1.5in. I think the transom was replaced before and by doing 1.5 in over what was there they didn't leave space for glass on the inner skin, make sense?

I might go the arjay route. It's something around 7.3 lbs per gallon, but how does that equate to the weight difference of what I took out of the transom? Is it going to be slightly heavier ? Lighter? Or about the same?