Sorry, Not a thinking day, but since I can not see your haybine I do not know what size lift cylinders you have, but if you have like a pair of double acting cylinders longer than the standard ASAE 8 inch stroke you have more oil comming out of the cylinders on the lower stroke than you do on the raise stroke. Also if your rate of drop is too fast the breather can not handle the sudden rush of air or if the breather is plugged the dip stick can pop up. Make sure you can control the rate of drop, Too many of these restored tractor guys take the restictor swivel off (one less place to have a leak) and then there is no way to control cylinder speed. In time you can also caviate the cylinder and you do not need these metal particles in the hydraulic oil/ Confused send me a U-2-u