Sorry not to reply sooner chaps, but I missed this thread too!

Thanks for the compliments.
The main modification is the addition of the centre sill and new brake gear. Because freight cars in the UK used hook drawgear and buffers, their underframes differed from freight cars designed for automatic couplers. And the brake arrangements differed, as UK railways used vacuum brake -rather than air brake - until fairly recently.
Japanese four-wheel freight cars were an interesting hybrid of UK and US practice, which is what I want to demonstrate with this model. I managed to do a bit of work on it the other night at work. I'll post some more photos as it gets near completion.
Cheers,
Mark.