You have to "Go Advanced" (button below the edit field) and then "Manage Attachments" (below the edit field in advanced mode) to add pictures, if that is the problem. Manage Attachments is a bit tricky, we had to discuss specific problems and see.

But the IM pictures are not absolutely needed here, we can see them directly on Wikipedia. Another web page describes in the text that the IM even had kind of rails in the fuselage and a trolley so the crew members could reach their station in no time. I think they mean the tail gunner in some versions, who was a noticeable tail load which could be borne by the stab only (I think).

I didn't find a biplane calculator as well but that's not the biggest problem. The only three-view I found is too small and I don't know if it's the version Sal is building, so he had to supply a suitable three-view if we wanted to do our own calculations.

What I did so far is only
1. translate some of the text in the book clipping,
2. interpret the sketch,
3. cross-check the details in text and sketch,
in order to see if I comprehended things.

Last time I translated a Russian technical text was 40 years ago, that made it a bit hard but interesting. The clipping left only a part of the reasoning for us to read so the whole context is lost. Therefore it was not possible for me to really construe the statements in the text.

That's why I simply made the assumption the IM was really set up like described (or what I think is described). Otherwise it could be a what-if analysis in the book as well.
Then I assumed in addition that the few figures given in the clipping are quantitatively correct.
Finally, the balance and the neutral point were calculated/estimated. The NP calculation could not be reproduced completely. (Maybe they factored in the reduced biplane efficiency, we just don't have any information about that in the clipping.)

Result:
These simple calculations at least didn't prove the assumptions outright wrong.
So the IM could have been really set up unstable like shown in the sketch (NP ahead of C/G). We just don't know.
Even that wouldn't be the end of the world, though. Still an average pilot should be able to handle the IM.
That's my assessment, of course, based on the fact that the model is a huge parkflyer (see spreadsheet).
A lock-mode gyro would handle it in any case and would make setup problems (finding the balance point etc.) non-critical.
Period.

That's what I managed to squeeze out of the little information we have.
Anyway, if that's correct, a free-flight test model wouldn't work but using the stabilized real model for tests is easy.
Assuming that, one can ask if calculating the NP (actually a complete stability analysis) is worth the effort.
I'd think not, but I'd still do it as a hobby, provided Sal has a three-view and I find the time.

Burkhard