Hi Everyone
Here is a small update on progress.

Last couple of months have been busy at work, but I have been able to spend
some time thinking about this project.
The best source of multi winding inductors I have found so far is the
Versa-Pac series from Cooper Busman. They come with 6 identical windings
and properly connected they will give me a 1:5 autotransformer.
In theory this will reduce the duty cycle from a whopping 97.5% to the
somewhat more manageable 86.7%.

I have spent a considerable time reading about different kinds of snubbers.
Just when I thought that I had found an optimal way of designing RC- and
RCD-snubbers for the switch and the rectifier I got notice of far more
modern alternatives: active clamps.
But so far I have only found one such controller that can be driven from a
5V supply, but the carrier is not very easy to hand-solder, and in any case
the maximum duty cycle is just 74% due to current-mode implementation.
I guess that a good old voltage-mode controller will have to do. My
requirements on the quality of the regulated output is not very high anyway.

When I look at the few exemples of tapped inductor boost converter that
provide any kind of schematic I have not seen any kind of snubber at all,
except for the secondary side rectifier diode.
Is this just a simplification for sake of presentation clarity, or can it
really be omitted?

My plan, so far, is to draw snubber networks for the diode and switch just
in case, and just don't put them on the PCB if they prove redundant.
With some strategic test points I can  measure the leakage inductance of
the autotransformer and this should be a good starting point for an almost
optimal design.
It seems however that the leakage can be measured in different ways. How
would the members of the group proceed with such measurement?

This became quite some texts, but I guess that my main questions at this
point boild down to: