l read some reviews and people talked about putting ducktape on the overlap and the edges.Is this necessary?

l dont use liners-

go with the kevlar reinforced tubes filled w/ tire goo. Unless you run over something catastrophic, you will be fine

It certainly helps to hold it in place long enough to slip the tube over top of the liner. You do not need to load on the duct tape, just a few here and there, electrical tape works well too.

Forget the tape crap, that only make u look like more of an amateur than me. When installing these liners, here r a couple of things u will need to do this easier. A flat, raised surface to do the installing of the liner, & a surface that will hold ur rim horizontally in such a way to make it easy to put the tire on the rim (empty circular trash can works well for this). Put the tire on the flat surface, install the tube at this time with a little air in it to hold the liner in place. Put the tire on the rim. It sounds easy but u might have to practice this stuff to get it right, l sure the hell did.