[tartuffe]

Those jack plates are really nice. If you keep the transom intact, you will need the 10" extension to provide engine clearance when you trim the engine back.

I also have an 81 20' that I just took apart. Pics are under "here she is." I gotta say that while my boat may be the exception rather than the rule, for the amount of wood that did not have glass on it at virtually every cross-member, I would find it hard to believe your stringers do not have some issues.

I hope I am wrong but with that said, if you cut the back end off that cap and then find you need to take the cap off, you now have even more work to do to fix that cut. Also, you are now going to need to do nice looking work with grinding gelcoat back, fairing, in multiple radius. Taking the cap off on these boats is not a complicated process provided you have a means to lift it whether an engine lift or a come along over a branch. It probably weighs 400 lbs and is pretty stiff.

Regarding estimating materials, plan on wetting out 36 SF of 1708 with each gallon of resin. Plan on at least a half gallon for attaching the first layer of ply to the transom skin and then another 1/2 gallon to glue the 2nd layer of ply to the first. I also used 2 $20 bags of cabosil, 1/2 gallon of ground glass fibers from US Composites and around 3 quarts of 1/4" glass fibers. (all of this went into that gallon of PB mix) You will need two sheets of 3/4 ply as well. You can only get 1 layer of ply out of each sheet if you do not plan on cutting it. I found a $3 trowel from lowes with1/4" gap with every other tooth broken out worked good for spreading the PB with the 1/4" chopped glass.