Building fold up trailer

Hey explorers,

Im a long time lurker on these forums and now i have finally joined in order to ask a favour.

We just did 18 months on the road in our caravan and are gearing up and saving money to have another go at it before the kids start school.

As you can imagine with a wife and two little ones
I am constantly looking for ways to save money.

I cannot go exploring again without a fold up boat trailer for the car topper.....so ive decided to build one myself.
I have a fabricator / boiler maker friend who will inspect my work but apart from that I'm on my own.

Does anyone know any information resources i could tap into? And heres the big favour.....

I am wondering if anyone in the melbourne metro area has either a mangrove jack or dunbier (newer model) alluminium folding trailer.

All i need is to spend 2 hours with it in ur driveway so i can wrap my head around it and get a few ideas.
I will be basing the trailer on these two models because they are the lightest but will need to change it and create my own design as our car topper is too wide for them (and copyright trade marks etc)

Any help is greatly appreciated and will be repaid in drinks of your choice.

Cheers

Phrankia (Nick)