Mikkel has already posted a link to my thread on the old RMweb - where I used parts from a Hornby Saint body to kitbash a model of a Star. These are a few of the more major problems I found with the Hornby Saint body moulding:
Over long smokebox
Too short firebox
Safety valve cover in the wrong place
Splashers too shallow and incorrectly spaced
Front buffer beam is way too high
Cab shape is somewhat dodgy
Most of these fundamental dimensional errors seem to be due to the body being designed to fit the old Tri-ang chassis with its incorrectly spaced (and sized?) driving wheels.
I think it would be simpler for Hornby to do a Star than for Bachmann to do a Saint - the Star and Castle's chassis are almost identical - whereas the Hall has the smaller driving wheels, 6' as opposed to the 6' 8 1/2" of the Saint, Star and Castle. Some of my favourite prototypes these, but there's never been decent RTR Saint or any RTR Star ever - even though all were fairly long lived, successful and survived into BR ownership. Just overshadowed by later, more famous locos I suppose so they get overlooked.
I still need to finish off the tender for my Star - one day I will when I get the time!