The sticky film on the tape supplied will adhere to the mylar head of a cu"mbu"s, - I have not tried the newer "fabric" heads- but use a tiny bit at first to try a few locations until you get the tone you want. The placement of the pickups does affect the sound.
I new one guy that installed them on the inside of the head!
No problem with the contact on the head, though. Also works on yayli tambur, cu"mbu"s saz, etc.
On oud also try the placement thing until you get the tone you like best. It's hard to internally mount them, but I have, if you carefully remove and replace the rosette.