There's a photo somewhere, which is not mine, and maybe from the site, of the Lyons tea container on a flat wagon, possible 273XX series. The container seemed to be shorter than the wagon by about 18" each end and just sufficient6 to engage the cuplocks (if that's the correct terminology) on the flat. There is a 'broadside' and a 45 degree oblique shot. If I can find a copy and no-one has any objections to me posting it without credit. I will do so. If you can determine the length of the flat over the headstocks, you should be able to get scaled dimensions