ORIGINAL: ec121
Engines designed for the European market are made to run on no nitro. European fuel has no nitro. The Supertigres were designed in Italy. They shouldn't need more than 5% to run correctly.
Yes, I run mine almost exclusively on 5% w/o any problems.
However no matter the above "fix" was still required on some ST engines.
Though ST was originally of Italian design and manufacture, the Chinese plants took over some time ago and there were many modifications done to the engines.
I doubt that as such they are "designed for the European market" with the Chinese production.
Hobbico/Tower is the biggest seller of these engines and now owns ST
AFAIK.