I'm setting up Crossfire on my transmitter and some quads. I'm concerned about how flimsy the T antennas are. Would it hurt the performance if I heat shrinked them or heat shrinked some zip ties to them?
No this not an issue. It is a common way to attach the immortal T antenna. Just make sure your antenna is not running along the frame. make sure the antenna is perpendicular to an arm or sticking out away from the frame.