will this idea work?
 

if i take the spring on a two pronged rest and reverse it, (the spring that pushes the rest up), so it pushes the rest down, then tie the rest to my cable slide so it can pop up at full draw, will this function as a drop away?
also, when do you want a drop away to drop? ( at the beginning or end of the arrow?)
thanks

RE: will this idea work?
 

Not quite sure just how you'd make it work. I haven't tried it but that's basically what the manufacturers do so it's got to be possible, and for a lot less money.

You want the rest to come up to it's upper most position about 1-2" before you reach full draw.