forestdon hasn't actually said what precise categories he has tried, but I am pretty sure that the reason he has been unable to get the custom postage option to come is because is most probably that the categories/sub-categories he has tried are for some reason not included in SD exempt. It seems to be that although the overall coolectables category is included in those that are potentially exempt from SD, there are some sub-categories which are excluded.
I only got the custom option to appear by making the trial listing in the general postcard category (and I doubt very much if that would be suitable for specialist postcards like railway locomotives), but when I tried to refine it to a more closely defined category (as forestdon had done with his now ended listings), that option was taken away.
I would find it hard to believe that his account is behaving that differently from anyone elses, and think that there is an issue where some sub-categories which should really have the SD exempt option available (ie. the postcard sub-category within Railwayana), are being excluded because a category higher up the category tree they are listed under, is not exempt (in this case the Railwayana category).
