I totally agree with david. My brother knows about the DL, and he still can't tell when I do it.
But I've just started to use the pass, and doing a lot of false cuts. I still do the DL, but I never do the same DL twice, which is a little hard to do, but it keeps the hecklers quiet.
So learn some more DL's and pratice in front of a mirror everyday.
What I do is try to use more than 1 type of DL, and sandwich a few tricks in between them, that do not use DL's say something with an Ascanio spread or Elmsley.. I have two different ways of twisting the aces... I alternate them in case I see someone that saw the elmsley version,...
I guess what I am saying is, do not rely on the DL as much, and always keep them guessing by using different methods.
One last thing you can do that i am going to try is, buy Card College Light, and learn a few " Self Working" non sleight of hand routines. This way they can look and look to their hearts content and not see a single sleight. THAT would be magic