The addition of "three full sizes" to LOF in order to establish SLL is an old, old convention. It works...kind of...for mid range sizes and mostly men's shoes.
But a "full size" is always one immutable thing--usually one third of an inch.
So to Sabbage and a lot of other makers, it quickly became clear that three full sizes was a larger proportion of a very short foot length than it was of a longer foot length.
In my experience, that realization is just about the most reasonable concept that has ever been imagined esp. because it can usefully be applied to every foot.
And that brings us to whether the same technique apples equally to men's and women's feet/shoes.
The question is "Why wouldn't it?" The whole concept is tailor made to deal with relative proportions. If a man's foot is very short why would you apply a different standard than if it were longer. If a man's foot were as short as a woman's foot, what changes? If a woman's foot is as long as a man's foot why would we treat it differently? The nub of the thing is that Sabbage's Sectionizer deals with feet rather than gender or convention.
I suspect that the convention of regarding men's and women's shoes differently comes from manufactured RTW shoes and standardized lasts, and is a kludge to deal with those relative proportions without having to actually deal with the implications. Bespoke makers deal with feet, manufacturers deal with lasts with little to no regard for actual feet.
So...your second question. This can be a matter of judgement. First, the chances are good that your customer has never had a bespoke fit and is used to wearing shoes made on lasts that are mirror identical. So if the discrepancy between the footprint and the bottom paper is not too great, it can be ignored as long as the girths are correct. The upper may 'overhang' the insole slightly but the shoe will not necessarily be uncomfortable. Of course, this assumes that the ball girth on both feet are correct...or near-as-nevermind.
I,personally, have great respect for the medial side of the foot. Barring foot problems, the foot will not spread to the medial side much if any. A normal foot and a normal gait pushes the bones and the flesh laterally simply because that's where in the gait that most of the weight of the body is carried.
So I always put most if not all of any wanted build up on the lateral side. My teacher always said 1/3 medial, 2/3 lateral in reference to building up in the forepart (specifically the toe). I tend to generally agree with that formula although I might favour the lateral aspect a bit more. It's a safe formula, in any case.
In this particular case / foot, I would line the bottom paper up with the medial footprint at heel and joint and let the toe print on the medial side peek out form under. No harm, no foul.
At the same time the large toe can overhang the insole at the side somewhat...not egregiously so...and especially as the heel height rises.
If I might make one other observation: I never try to square the bottom paper with the outline--not lengthwise not width-wise. Outline generally gives us information about flesh above the plantar surface of the foot...and correspondingly the insole...and can be misleading with regard to LOF. once I find the LOF i bracket the footprint and align the bottom paper between "0" and "12". The outline will usually be well outside the proper positioning of the bottom paper, lengthwise.
Hope that helps...it's early and I haven't had my coffee. And besides that I'm old.
