More and more applications seem to be capable of using the OpenType ›size‹ feature found in some fonts that come in different optical sizes (e.g. Adobe's ›opticals‹, or the Latin Modern fonts). I can't seem to be able to implement that feature to a font I'm designing, though. FontLab, for example, will let me add and save it as part of the .vfb file, but loses it when generating the actual OT file. It won't properly read the size feature, either, when loading a font that has it.
What other ways are there to add it to (a) a font in the making, and (b) to an existing font? Thanks in advance!