Tunturi
You may like to get your QRH out again if you are still on type. As someone else has mentioned earlier high trust settings are also a factor and climbing thru FL290 will be full rated climb thrust. Compound that with the nose up attitude and suction feeding is sounding marginal at best.
Subsequent to this Boeing issued a bulletin to instruct us not to crossfeed in any other situation than cruise. Going a bit far for a cover up I feel but I have been wrong before.
