170 degrees movement? What?
What speed servos are you using?
Instead of going to 80% ATV, why don't you go back to standard horns and put a 6v pack in? ( i take it you are not using one allready).

From what the Boy has said i might be able to get the AoW of the Moki 180 and bits e.t.c similar to malcolms YS 140 setup by using a carboncopy spinner and justengines carbon prop.
If i could get the All up weight of a 140 down to around 9.5-10 lbs with a 180 pulling 20lbs............... :bananahea !
Not that i would recommend such an act.