Maybe a bit late responding to this thread - been away from puter for a while.
Very interesting to see so many ideas on building your own trailers out of caravan chasis etc.... but if you are planning to use it on the road then you are breaking the law.
Some facts that some don't realise.
A trailer must have a load rating plate ( like a car VIN plate ) . Home made trailers not inspected and without such rating plates are not permitted on the road.
An unbraked trailer may have a maximum rating of 600Kgs. That maximum loading
includes the weight of the trailer.
A nissan Terrano towing an unbreaked trailer more than 750Kgs, despite the fact the Terrano is rated to tow 2800Kgs is breaking the law.
A nissan Terrano towing
an empty braked trailer rated at 3 ton is breaking the law.
Years ago you could get away with alot...... these days you just can't risk it, the police are heavily clamping down. Two of my mates have had points and each had over £1,000 fine.