in the meanwile I have these
www.pvr-modelbouw.nl/XXFT-EU.pdf
www.pvr-modelbouw.nl/XXFT-US.pdf
just print the pdf on a A1 sheet of paper. cut out the parts. glue them to a sheet of 1mm alu or steel. cut out again. fold the dotted lines and gleu, bolt of rivit the parts togetter. add the axles of your scale. and you have a trailer chassis