John reading your reply above I see where you are coming from but and there is always a but if you look at the market there are very limited amount of people modeling 21mm compared to 16.5mm. Someone said in an earlier post that there is another site with a lot of 21mm modelers on it but the fact is the discussion is happening here and not somewhere else so I can only comment on the majority of members on this site which model 16.5mm.
At the minute on this site we have 381 members now out of that there is only yourself that I can recall (I may be wrong and stand to be corrected) who has posted up 21mm topics photos layout etc etc which are fantastic and I love to read and study your work as it does give me an insight into 21mm and there was someone else who was doing a thread on building 21mm track. Then there are others who do a lot of talking but thats all they do.
The point I am trying to put across is I don't see why if a manufacturers asks the question what would you guys like to run behind your MM locos I'm thinking of doing a run of something, that if accommodating 2 members it may push the cost up for the other 379 members (and remember I'm only talking about this site) it don't make good business sense to go down that road.
Leslie asked in his original thread what would we like, Arran as we know is already working on a wagon. Now if they can do something to accommodate both 16.5mm and 21mm and keep the cost down I'm all for it but if they can't well then it has to be majority rules and that is 16.5mm.