Are toppers easily detectable to touch? My opinion is yes. You can get a pretty close fit with almost no edges lifting. With good attachment you can get almost no lift on the sides. If you're wearing a topper and someone wants to find out all they would have to do is slowly run their fingers in an itching pattern from front to back and feel for a difference in texture. That being said. Someone would have to have her hands in your hair a fair bit to figure it out. I have female friends who constantly touch my hair. Some like to mess my hair up, others prefer neaten my hair up. I haven't told many people I wear. I belive most of the girls who mess with my hair are oblivious to me wearing. Unless you have people who like to massage your head I wouldn't worry too much about detectability to touch. Some of the guys on the site who wear toppers live with girlfriends who are unaware that they wear.

@JRob, I think your pieces are the bomb. Gell isn't for everyone, but to say someone who puts gell in their hair is greasy is like saying girls who put makeup on look like barbie dolls.