Hey arccaster,
Welcome to TDH! You'll find lots of great info here on doing a costume.
Congrats on your first helmet! If you use the search function and just type in rubies, you should come up with lots of threads about those helmets.
One thing I've read about people doing is epoxying a metal "craft ring" into the bottom of the helmet. It's the type of ring used for embroidery or needlepoint. From what I've read, it helps to keep the helmet's shape.