I tow a twenty foot twin axle van with a 1998 Laguna estate and am limited to 75Kgs for our nose weight.
Due to the layout of the van most of the serious weight is over the axle area (kitchen and wardrodes). Then there's the rear double bunk room, which houses the awning (875cm) under the bottom bunk. We use this smaller awning as a 3/4 awning as it is plenty big enough.
Now while I agree with Lutz that excessive bulk weight at the extreme end of the van is not ideal, sometimes you are left with little choice. But by keeping the weight as low to the floor as possible we manage to tow without swaying or nodding. With minimal weight under the front bunks and again by putting the heavier items to the axle end of the bunk lockers, we have got to our target weight of 75Kgs.
Once you have found by trial and error, the best loading plan to achieve the tow criteria then I'd suggest you do a basic plan sketch, then the kids and all will pack the van to the same plan each time.
As we caravan as a family group I often have nephew's and niece's wanting to help pack the van on site, so I hang my packing spec on the open main door so that as the kids file in with the goods they can see the plan and go to the right locker to store the items.
I have found that by using higher nose weights that the brakes tend to be more sluggish to operate and I put this down to excessive friction on the hitch due to weight bearing down on the sliding shaft.
75Kgs does seem to be a nice weight to get the close coupled brake system working effectively while also not making the car look arse heavey.
Steve.