Thanks all. I didnt think they would be that strong, but they are!
And I literally put them together with screws and tools I had in my toolbox, after picking the strongest looking pieces of wood from the furniture I had previously smashed up! I glued blocks of soft foam around the ankle holes, and then covered it all in old curtain material from the attic (mainly to hide all the screws, hammer marks and holes I drilled in the wrong place! ) A bit of a lucky botch job!!