The distance other ships can follow you and actually jump seems to be completely random. I built a ship to mine that can jump 7.2 sectors. Sometimes it won't follow even 3. I check to make sure it it charged, fully manned, and not damaged. I've had it jump all 7 with me and then it wouldn't even follow me 3 for a while. Then randomly it did follow me 3 again. Is there any reliable way to get it to jump with me?