They are BIG - I bought a secondhand one at the Stafford show here earlier in the year for £90, mainly for the possible reuse of the two motor blocks, but it was too nice a model to break up, even if it dwarfs all my other stock!
Dimensions (roughly) in Imperial are Length 15" (+ couplers), Width 5 3/4", Height (above railhead) 7 1/8"
It definitely doesn't like Radius one points when coupled to stock, though it negotiates them OK without stock.
No problems with the A/craft large radius points or 4' and 5' radius curves