Scarf joint and nut compensation

[Abstraction]

12-string build in Tassie sassafras.
Scarf joint reinforcement?
1. 15° scarf joint angled towards the headstock, not the body.
2. Headstock will be 10mm piece with scarf joint, 3mm facing which will reinforce the joint. (These are not to thickness yet. Total headstock thickness 13mm for Gotoh sg381s I'm thinking.)
3. Looks really flimsy. All that tension...
4. I'm tempted to run carbon fibre rod across the joint, 1 or 2, under the facing.
Question: Is that overkill?

NUT COMPENSATION
I'm about to mark placement of frets on fret blank. Came across video by Susan Gardener. (https://youtu.be/a9A_yQ4Odog?si=PPlT3JnoMEA2k1Bo from 8:30)
1. Fretting a string raises tension and pitch slightly.
2. So open strings can be relatively flat. Small but measurable.
3. Some compensate by moving nut forwards. B/w 0.5mm to 1.5mm. (A compensated nut accounts for individual strings. No thanks, not on a 12-string).
4. Some shorten the fretboard. The minimum compensation needed is generally about 0.5mm.
Question: is this overkill? Should I shorten the fretboard by 0.5mm?

I love that every step in instrument building is a new Pandora's box of things to learn. Or maybe a box of wisdom hidden beneath piles of perspectives and lessons learnt.

[kiwigeo]

Re nut compensation. When I don't compensate individual strings I shorten end of fretboard by 0.3mm.

If you want to get into the nitty gritty of compensation at both ends of the fretboard Id get a hold of Gore and Gilets Books. Trevor clearly lays out all the options for nut compensation.

[TallDad71]

Regarding the scarf joint.

I’m sure it’ll be just fine. The thickness of the headstock at 13mm isn’t really a factor, the maximum most machine heads will let you get to is less that 16mm, so you’re not that far off.

The 15° scarf angle is usually quite strong. I always favour the 10°joint as you get more gluing area in the scarf joint so it feels a bit more solid. I never really saw much argument for having the extra five degrees anyways.

[Abstraction]

Thanks for that, Martin and Allen

[56nortondomy]

I'm about 70% into a 12 string build at the moment, I've made my headstock thickness 11mm and I have a veneer on front and back which beefs it up to about 15mm. It also has a 15deg scarf joint.
Wayne