Certified limit is 43100ft and MTOW is 569t.
From SIN to LHR (FTI 13:10) the other night at around TOW of 550t (if I remember correctly), we went straight to FL340 which, by the time we got there, was a few hundred feet below REC MAX. The plan had us initially at FL320 with a climb to 340 about 1:15 into the flight.
With the climb derate taken out, the climb rate was near 800 fpm for the last bit.
Got to FL400 in about the last three or so hours before LHR.