Lower and midships is the best option. The higher you go on the ship, the more pronounced the motion is. The same is true for fore and aft., the closer to the bow or stern, the more affected by motion. My wife is prone to seasickness but uses the patch and has no problem.
Western Caribbeam Carnival 2005
Eastern Caribbean Holland America Zaandam 2006
Alaska Diamond Princess 2007
Western Caribbean 2008
Southern Caribbean 2008