Where is the particleData sizes[] actually used to scale

I'm changing the particle class to allow me to scale itself each tick, exerything is fine except at the moment I'm having to change the F32 sizes[ PDC_NUM_KEYS ] in the datablock each time I want to scale, this is obviously not waht I was as this is changing a datablock and is global to all the sprites. Normally this would be easy to add a variable into the particle class to deal with scale, but I can't find where sizes is actually used by anything to change the scale. It DOES do it, as like I've said I can update it and the changes take place ingame. but where?