Not sure what your existing payload is (Rapido have a reputation for being a bit minimal as standard) but you'll lose a valuable 200kg if you downplate. That may even make it impossible to use without technically overloading.
As Neil says yes it is easily possible, if costly for the paperwork, but the payload is the concern, there must have been a reason it was uprated in the in the first place.
My dads motorhome was uprated from 3500 to 3850, but the only physical change was to put 16" wheels on instead of the standard 15".
Thanks to you both. I have no idea why it is plated at 3.7 or who did it. It may be that is was manufactured at that weight.
The only reason I was considering the change is because I am selling it and I feel it may be putting buyers off, especially the more mature buyers (like myself).
If I don't sell, then in a couple of years I will have to do the necessary for me to continue to drive it. (Reaching 70)
It was probably set at that weight to allow for the stuff you carry, if you take it to a weigh bridge, you will see if its over 3500kgs, which it may well be. My local sand and gravel suppliers charged me 4 cans of beer to use there weigh bridge.
Be careful about down rating as Essex Police recently had an exercise and pulled off a lot of motorhomes and caravans 2 were fined a lot of money and if you are overloaded what do you do with the stuff you have to take off before you are allowed to continue your journey ?, if you are thinking about down plating because you have reached 70 it would be a lot cheaper to pay for a medical than getting fined.