Not scaled one before, but would a 40ft skelly with a chopped down 45ft container not be a good call for this. That way, when the bed gets corroded you just buy and chop another 45ft box, you can lift off the bed for thorough cleaning of the chassis to improve life too.
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I think that is a bloody good idea… 
Be too heavy. Trailer chassis plus container base.
Personally never had a problem with my spread axle tandem cartwright. Ex thermalite so built for heavy work. You need to specify your trailer for it’s use. Buying s/h is a minefield.
By the by them tandems ran well at 44tonne! 
We use Pacton they are absolutely bullet proof although not particularly light