A question about methadone switch to suboxne?

been on meth 30 mgs for 8 yrs. stopped 5 days ago .dr has me using roxicodone 15 mgs to tolorate the w/d's . tonight I am to stop my last roxi 15 at 10 PM and then go to Dr. at ( am to be put on subs.at that time i will have had no meth in 120 hrs. and no roxi's for 10 hrs . it has been very tolerable but today is a bit rougher that the past days. My question is if I take a 30 mg roxi will it also be out in the same time a 15 mg roxi would?? does the mgs matter or is it the time without that is important? dont want precipitated w/d's after coming this far. any advice from someone with experience in this matter would be greatly appreciated. Thanks, drew vachondrew@yahoo.com