I did the safety pins method for my friends ears
. (Mine as well but in the end I also hot glued them down as well lol)
I sewed in fabric loop in the same colourmas the ear to the under side of the ears. 4 of them so that they would I could slip snuggle the safety pin backs through so that pin section was left outside the loop. The size I use was round the 2cm length ones the second smallest size you can get.
All though in hind site I could of done a head band consider how LARGE the ears are.