IMO....you will do better to NOT use the suboxone to lessen the w/d from percocets. You would be better off just going through the roughly 5/7 days of percocet w/d. Eventually you will have to stop the suboxone as well so I don't find that trading one drug for another does any good.
I'm assuming that your not going through a dr to get the suboxone, since your asking for info for when to dose. Here's something you definatly need to know....if you take it too early you will be sick as a dog! Like deathly sick so be very careful. You must have everything out of your system for AT LEAST 48/72 hours before you can take the suboxone....and I'm not quite sure how you would know that?
Honestly, having gone through BOTH of these w/d's, hydro's and subs, I would take the hydro w/d ANYDAY! If your really looking to quit you can do this!