I quite concur with the weight senario.
We tow with a 1998 Laguna 2Ltr. The hand book is quite confusing. We work with the Gross train weight as the Renault dealer has suggested which of coarse is the legal tow limit for the car anyway.
Renault have probably put quite a few people off in the past by their vague terminology which is suspect got lost in translation.
Every Renault I've owned from a 5, 11, 18, 25 (X3), 21 savanna, espace (X2) to Laguna has towed to it's max capacity and done so very well indeed. In fact I've said for years that the R in Renault stands for reliability.
Our combo of a twenty foot twin axle van behind our Laguna Estate looks a bit over the top visually but is quite legal weight wise. Drive ability is very good and our outfit can hold a steady 40MPH in third gear going up Black rock, which is the steep hill approach to the heads of the vallies road between abergaveny and Myrther. I don't have any additional cooling fans fitted to the radiator but do use the air con when towing as this pulls in the two factory fitted fans anyway which provide more than adequate cooling.
A tow of 900Kgs is well within the capacity of a Scenic diesel.
If your concerned about the legalities pop along to your local heavy goods vehicle testing station and there you will find the vehicle inspectors are only too keen to help. After all they are there to test vehicles and the opportunity of not being seen as the bad boys realy makes their day.
With my outfit being so close to being over size/weight, I did spend a fiver at our local public weigh bridge just to get a ticket that shows I've taken the care to know what the combo weighs. Obviously it is only a guide but often on producing that and explaining my thoughts to an officer of the law, I get a friendly smile and after checking the car and van out, I'm left to continue with my holiday. I've only been checked a couple of times in 6 years and that has been the out come.