Like others have said you need to ask your PH for photos of buffalo taken from area. Some areas 40” is an exceptional bull and some it can be an expectation. Luangwa is known for good buffalo, but only your PH can really answer. Also, there are many factors in a wilderness hunt. Buffalo numbers will change in concession daily and at different times of year. Hunting in May(?) could be a difficult hunt because the vegetation isn’t down yet like later in year. Sometimes you can hunt for an exceptional bull and sometimes passing any hard bossed bull might be a mistake. In general, anything over 38” is considered a nice trophy and under 35/36 is considered a non-trophy. Anything above 42 should be considered a great bull. Planning to hold out for above 40” and harvesting a 44” bull will only be predictable on a game farm (except for a few premier areas). There is a huge difference between hunting a game farm and wild area. You take what conditions at the time actually allow.