Many thanks for your very informative post. It is so hard to get information about Altai and other places in Russia in the English language. So it looks like we do not need to take the 10 hour bus ride from Kosh Agach to Gorno-Altaysk but can break it into 1 or 2 night stopovers in between. I think there will be marshrutka or taxi chances on this route.
I think I know what you mean about American passport holders, Igor. With all that is happening lately I imagine many Russians would be angry at the US, and they have some reasons to be. But in so many visits to the old USSR between 1978 and 2012, hostilities from Russians, or Soviets, have been very rare (sober guy on Trans-Siberian near Omsk in 1978, drunk guy on BAM neat Bratsk in 2012). People were hostile on the airport bus in Komsomolsk na Amur in 2012, but mostly Russians are nice or indifferent to foreign tourists. Siberians are nicer than other Russians, if I had to make a judgment.
I believe you are living near Omsk, which is a nice town. I have been thee for 30 minutes twice, in 1978 and 2010, and scampered around to see as much as I could.
We plan on flying from Novosibirsk to Prague or taking the train, probably the plane because we have done the rail before and the plane is cheap. Would still love to take taxi, bus and marshurutka from Tashanta to Biisk, then the overnight train to Novosibirsk. Maybe the obzhy, or ordinary berths on the Biisk train, what do you think?