Thank you Paul for reply,

i just received a SFS topper with long flaps, i have experience with a classic topper.
Usually, i attach my system with Ultra Hold, but for the flaps i'm looking for the best way. (glue or tape ?)
I tested to bond with tape, it work but i can see the lace along the flaps through the hair.
I think Glue is more secure but for the maintenance routine, i already spending lot of time without flaps on my system...