Yeah people don't know, methadone doesn't block or strip/remove opioids from receptors, that is misinformation. Methadone maintenance though is designed to build up such a high methadone tolerance that using other opioids (like heroin) won't really work. For a first dose keep in mind it takes a few hours to really get going, and you should be fine taking 20mg hydrocodone considering your tolerance, definitely don't go nuts though, and methadone has a long half-life, especially before your body gets more efficient at processing it. So if you take another 30mg tomorrow you will have still ~15mg in your system on top of the new 30 giving you more than 30mg in your system when it peaks. With this increase, and the way respiratory depression works, you can easily overdose, so be very very careful, but 20mg hydrocodone on top of 30mg methadone should be ok, let us know if it helped at all.