The stock screen is 390 tall x 380 wide, well, mine is anyway.
Willthe Fabbri clear the handguards? To be frank, I'd try the 'secret' 4th position and angling the screen back with spacers / washers under the lower fixings for the bracket first and see how you get on.
Plenty of other threads here, but the angle seems to be as important as the size of the screen..