Scale Specific Particle dimensions possible???

I can find no way to scale particles to the sizes I require. The only property seems to be the Grow property which scales particles in both 2D dimensions.

I really need to be able to scale particles by just a single dimension at a time.. Is this not possible?

There's no such parameter for particle systems, so no, it's not possible.

Is this really not possible to do?

you can vote for the feature here