I would move out on the control horn and in on the servo arm until I didn't have anymore room before I messed with the endpoints. Ideally you don't want to dial the ATV down until you have no more room to mechanically adjust,,, at least I dont. You should be able to get at least 125 to 140. With a Rocket City control horn setup I usually dont have any trouble getting it done mechanically so that I can leave the ATV's on the transmitter maxed out.