Would assume that the only way to increase max auw is to
1. Lengthen mrb's etc as per FF model However then have to slow blades down to stop tip going too fast. Easier solution add another blade.
2. Dont forget the 5 blade machines have a lower service ceiling as the certification is for flight at max auw. 2550lbs for 4 blades and 3000lbs for 5 blades, hence some of the decreased performance is due to higher auw.
Looking forward to those in the know answering other questions. I believe the melb as max take off of over 5500 lbs
