Ok, I think you are on to something because I have felt the same way. Tail pointed straight down = girl tucked to the side = boy. Now, I could be talking out of my rear here, but I have been watching my trio very closely. Shelly my youngest and smallest has s/he tailed tucked to the side all the time and is the bully and chases and bites my other bigger torts around. My bigger two Moe and Jay hold their tails straight down and they are mellow and enjoy each other's company.. Just my two cents..