You can adjust the elevator manually on the plane itself. I think the way the slo-v attaches to the elevator horn is with a screw-on rod attachement and then it clips onto the elevator horn. Simply unclip the rod attachment from the elevator horn by pulling back the rubber little tube then pull gently apart to release from the elevator horn. Then screw in or out to adjust the elevator. you will have to do this to both equally so count your turns or eye it up.

Good luck