I agree that flying with 5 skydivers would not be comfortable, safe, or legal in many of the low gross weight, under-powered Cessna 182's out there. However, adding a 5th skydiver to the load in a 300 HP wide-body C-182 with max gross weight of 3100 lbs can be accomplished within legal weight and balance limitations depending upon jumper weight, fuel load, density altitude, etc.
For a DZO, the option to fly with a fifth jumper can help with the bottom line. However, if the load has two heavy tandems... fly without the fifth. If the load is a ladies' 4-way and fuel is light... then adding a camera flyer might be just fine. On a low-ceiling day or with a student load going to 3500'... five jumpers might work depending, of course, on weights and environmental conditions (and any "crunch" factor would only last about 5 minutes... until the first jumper is away).
Manifest and the pilot would have to consider limitations of the aircraft for each load. From what I hear, there are numerous drop zones that operate C-182's with 5 + pilot. I am trying to find an operator with legal paperwork for that extra seat belt who is willing to share. Thanks!