Witr Behind A Shafi’i
SunniPath Answers (http://qa.sunnipath.com)

I pray this finds you in the best of health and spirits.

consulted a number of leading Hanafi scholars, including Mufti Rafi
Usmani (Grand Mufti of Pakistan), about this. Their response was that
it is permitted for Hanafis to pray witr behind Shafiis even if they
pray it differently from the Hanafi three rakats–such as two-plus-one.
This is based on a followable position within the Hanafi school that
what matters is the imam’s prayer regarding the validity of his prayer.

And Allah alone gives success.

Faraz Rabbani