I have a 7 mtr RIB now lying in Greece with 200bhp outboard as my profile indicates.
How many people I take on board it depends on where I'm going and most importantly what is the weather like and what will be on the return voyage.
When the RIB was in the UK (due to the unpredictable weather) have NEVER EVER taken more than 4 people o/b (although the boat can accomodate up to 8- comfortably). 4 people sit very comfortably on the two bucket seats the boat is very well balanced and cruised at about 45 knots and 3800-4000 revs.
In Greece, however where the weather is more predictable and the sea calmer (although meltemi can be of a problem in the Aegean) I have taken up to 6 people o/b to do about a 50 mile round trip.
There was a bit of a chop (wave height about 0.50 cm- 0.80 cm) wind SSW and the boat was cruising at 45 knots and 4000-4200 revs.
However, the people sitting in the bow section (specially the women) had a bit of a problem with their bikinies (u know what I mean. Don't you lads!!)
Any way, in a more serious tone how many people one has o/b a RIB (or on any pleasure craft on that matter) depends on the weather conditions and the distance one plans to sail.
SAFETY IS PARAMOUNT AND ONE SHOULD NEVER EVER TAKE CHANCES OR UNCESSARY RISKS.
An old Greek saying says
' ALWAYS RESPECT, BUT DO NOT BE AFFRAID OF THE SEA'.