Putting stitch holes in the leather layers with just a hobby awl was much easier and faster than with the latigo sole.
The toughest part was trying to close the gap at the heel. Because the welt is attached entirely on the outside, there's a hole where the back end of the sole, the back corners of the foot and the bottom of the welt come together. I tried to ameliorate this by whipstitching the welt to the sole using the preexisting holes that attach the sole to the foot. However, perhaps it would be better to put the welt between the sole and foot when they're first being stitched together, before the foot is turned rightside-out.
Firstly, the middle of the instep just before it meets the leg is too low and pinches the top of my foot painfully. This may be the result of my tailoring in part II where I wanted to get rid of excess material around the arch. I don't think that a softer leather would help, because the linen thread wouldn't stretch (something that must not have been apparent when the felt pattern was loosely basted together) and in any case this foot is already made from the relatively elastic part from the hide's belly. Only a fuller cut would really help. Possibly the curved stitch where the instep meets the leg should be cut higher.
Second, the toe is too low. That angle in the profile is my toenail pressing against the inside. Again, this may be because I cut away the "excess" length back in part II. If so, it may indicate that the original Missouri River patterns were, as I first suspect, too small. It's a very good thing that while I did mark the felt pattern with the revised lines, I didn't trim it, so it still has the pre-tailored shape. I will have to go through the entire bootmaking process again without the extra trimming and see if I can confirm these suspicions.
Lastly, aesthetically, the brown color is too dark and the "natural" linen thread too light, making for a very odd look with the bright line cutting across the leg just above the ankle. To achieve this kind of very dark brown, a hide would either have to be heavily dyed or smoked for an excessive amount of time. I think that a more natural smoked color (buff, goldenrod or golden brown) would make these boots much more plausible for portraying a person of middling economic status. Many buckskinners say that white leather was historically preferred for special occasions and that most leather would have been smoked - perhaps the Chärchän Man's white boots and red jacket were the equivalent of being buried in a formal suit today. The fil au chinois "natural" is off-white, whereas unbleached linen and hemp are beige - however, I'm not sure where to find truly unbleached linen thread at this time. Regular brown may be another acceptable option not because it's necessarily more correct but because it would stand out less.
In conclusion, while I have the basic steps down, it's clear that more experimentation is needed to turn out a pair of wearable boots.