It's a pleasure when it works!
My experience balloon and kite (Spountnik
loads tests a few years ago, launched since MIR, a great thing too!):
Do not use plastic wrapped wire (static electricity, several KV!).
Do not forget a resistance (~ 500 K Ohms 2W)
between the antenna and the ground otherwise it is very unpleasant!
I hope to contact you this winter, here I use
a kite (6m ²) and aluminum wire (1.6 or 0.8mm diameter). Tests have been done on 160m and it works very well,
I hope to reproduce these tests on 136 KHz (QRSS and normal CW), always
with a kite (helium and the balloon are too expensive for me).
VY 73 Alex and thank you again for the report.