Steve, what's supposed to happen (I should try this with dial gauge) is that a single piece of work going in, passes under infeed roller, so table moves down a few thou on that side, levelling up when work is under both rollers, and then tilting slightly to the outfeed side when work leaves the infeed roller. Mimic by pressing down on infeed side of tble first, and then outfeed, so as to cause a few tho of wobble. If table fixed, then (movable) head can move in same way. Inning and outing of work puts an uneven load on either table or head. Continuous feed can't stop any snipe at beginning of first cut but should prevent all, until the end of last piece gets a bit of snipe on exit.
According to the actual layout of the rollers and degree of wear in teh planer, the head might just tilt a fraction to the infeed side under the load of the rollers driving the stuff across the table. Again, dial gauge will show what / if unwanted movement is actually taking place as work enters and leaves cutting area on a particular machine.
I guess that pulling up on the work as it enters and leaves (if not overdone!) forces the other end down on the table as it passes under the cutter block, which must help a bit too, (unless your table elevating mechanism is very worn!)
