towers, when it goes lateral, does it always go left? if so you might try putting a couple of washers under the mount on the right side(as yur looking at it) between the mount and firewall, this will give you about 1.5 degree right thrust and will help it "hang there"

your servos are ok and i dont know much about your engine but i think the 13x4w would work well on a .61 2stroke

oh------ and to hover takes a lot of practice, a lot (to hover well that is)