Center of lift is a function of wing shape,the highest/thickest part of the wing is center of lift.To asume that center of lift is a certian %( i.e. 25 30 33) on all wings is dangerous. Find the highest part of the wing which is usually near the main spar on properly designed wings,when the nose falls at that point ,center of gravity is correct.On sweept wings center of lift will be the average of the highest part of the wing at the root and the tip. Center of gravity is always fwd of center of lift that way the acft remains nose heavy.Kiwi4