That would explain the difference in experiences. My balloon was 8' diameter at launch and expanded to ~40' when it burst at ~90k'. Mine needed the radar reflector and blinky lights. They were supposed to blink at a certain rate, but we cheated and had lights blinking faster as that's all we could find for our budget/schedule.

I would love to launch a HAB. I learned how to do PicoBalloons from a local group.