I’m a pencil and paper kinda guy - being the son of a draftsman I have an arsenal of paper, squares, protractors and compasses etc at my disposal lol.
I’ll give you a quick run through:
First off, I should have mentioned that my guitar is going to be a carved top. Also I have a wrap around bridge so height wise it’s almost as tall as a TOM.
The horn transition is curved (see progress pic) so actually following the body top is a little tricky so I’m planning on raising the neck from the body top somewhat ala David Myka’s double cut guitars as appose to cutting the neck angle into the whole upper section of the body where the fretboard terminates (that would slice most of my upper horn away) as to only have the fingerboards width proud above the body ala Les Paul.
I’ve cut a rebate (that’s English for rabbet BTW ) all along the edge of my body top leaving the foux binding at the desired height right around. Everything above just determines both the height of my carve and angle of my neck, there fore if I reduce the thickness of the body, the bridge height would reduce, diminishing the neck angle. decreasing the depth of the neck pocket would achieve the same thing. a little of both should shave the angle away nicely.
As this is my own shape and not an attempted copy of any one thing in particular, I’m willing to have a shallower carved top to reduce my neck angle if we feel this would be a benefit.
Old progress pic showing transition between bass and treble horns