You really are desperate to get on the beach with this thing aren't you ...
IMO the lightness denotes lack of strength ... the Jayco's are ok but not fantastic ie. they will still brake BUT they are around 750kg's ... so again IMO something that is 300kg's is
likely to have structural issues. Even an Avan is 600kg's (plus) and they have a habit of breaking up even when the bitumen get's a bit rough.
Does it have to be a wind-up camper? Do you have issue's about a normal camper trailer ie. 7x4ft trailer with tent top?
Scol.