First choice is to get on to ATC and get a clearance before leaving the 15M offset track, regardless of level. If you are unable to wait that long (can take 30 mins to get a new clearance!) then you should stabilise at a level between the normal levels, i.e. at a 500', before crossing other tracks whilst broadcasting on 121.5. Don't forget that there is other traffic not following the day's OTS, flying random routes and/or below MNPS airspace. Also don't forget that below MNPS is still class A controlled airspace, just with larger track separations because there is no requirement for approved nav kit.
Hope you never have to use it!
