pby & Rob : My 3 hard points were easy to make - I took the inside nuts off the towing eye in the bow and replaced it with a SS eye-nut. Did the same on the transom of my RIB with 2 more eye-nuts..
Between myself and wife we total just under 300 lbs. and I have a 5 hp 2 cycle (Nisson) that easily gets up on plane!! I assume that your 6hp (Mercury) is a 4 cycle??
A few thoughts
Ron, luckily I had welded tabs that I can use 3 inside, and 2 on the exterior of the transom up at the top. Do you connect directly to the eyes or do you have some kind of bridle that connects to the davit lines?
All up I figure 330lbs for wife and I, and 134lbs for dinghy and engine for a total of 464lbs. You'd think that would be okay, but...it feels like there's something is not quite right. With 3 adults, up to 80% throttle the speed increases, and from there to 100% no change in RPM or speed. Engine runs clean though, and starts on 1-2 pulls. But that's what people were saying to change the prop pitch... maybe stock it's to market top end for one person, and real world, you need a different pitch to let it rev out...