Hey,I'm on a transatlantic flight now and am at FL300 in my 747-400X. When I was at FL320 and FL340, the aircraft jumped around with altitude it could never stay constant at FL340 and would jump to like FL336 to FL344 with a large Vertical Speed. Is it something to do with weight or a bug? I should really be at FL380 but I'm not risking it lol - unless that will be better?My fuel/paylod are all fine and the ZFW was also fine. I have been using step climbs properly, but still the altitude doesn't settle.I'm using an unregistered copy of FSUIPC on FSX, and am I am wondering how to disable turbulence and wind-shifts, as I only seem to be able to remove all weather...I don't know how to solve this, my laptop can just about cope with the PMDG as it's not a gaming pc, so I am not going to by rex as it will just slow it down even more I think....I still want weather when approaching an airport like fog/mist/rain and some sort of wind... as real life, but in cruise, the weather just makes the aircraft go up and down all the time!Then sometimes, it is fine, it's starting to annoy me Any more suggestions and how to sort out the FSUIPC? Is this the altitude bug? Cheers!JamesIs t