That's about 70,000kg so would put you about half way to LAX. With a reasonable payload, FL370 would normally be regarded as enough- never FL410 with that much fuel and a payload as well. I suspect you are pushing the simulator (and aeroplane) outside its operating margin. You should have about 2 1/2 degrees nose up attitude in a comfortable cruise. FL410 is very rare in a 747- you really need a light payload and low fuel. It is usually regarded as economical to climb 4000' as long as you have at least 2 hours to destination to recoup the climb fuel in lower cruise consumption.