[quonie]

Well I'll be darn. I asked on another thread if anyone tried removing the wood core on the transom from the inside and didn't get a response.
What made you try this method?
Can you show a picture from the stern? Do you plan on building the transom up higher or close the whole thing in?
Your question on the fir. Better off using a high grade marine ply. As for a tool someone suggest a Fein Multimaster
on another thread in this section.Never used one myself but will try it out soon. Where are you located? Keep us updated with the progress