I collected information on the muro di Montelupone.
It is 1,6 km with an average gradient of 13,1% and one passage of 18% after 500 m and two passage of 21% at 1,2 km and one near the end.
There is one problem. There is crossroad at about 200- 300 m from the end of the climb, and from this point the road becomes one way (vehicles are allowed to go down).
You can reach the Piazza del Comune via another road but you skip the second 21% (and probably more) peak.
Despite this problem I am in favour to substitute Montefiascone with the Muro di Montelupone which is included in the list "The most beautiful villages of Italy".
Montelupone was the arrival of two successful stages of Tirreno-Adriatico in 2008 and 2009.
Gabriele
Gabriele