Having attended hundreds of Air Shows and experiences from sitting on the ground to collapsing a cheap camp chair and seeing all sorts of squatting arrangements. I can confidently recommend the Torii flight line squatter to you. It is compact, rated to 150 kgs (if you can fit in it, it will support you) and just as important in weights 1.2 kgs and will fit in your checked luggage.

If you are not happy with it within 3 months send it back for a full refund less postage and handling ($25).

The Flight line squatter is known as the best seat at any airshow.