Scaling particles across different aspect ratios

I discovered an issue while working on an iOS game using both particles and nGUI. We're trying to support both iPhone 4 and 5 portrait aspect ratios (2:3 and 9:16). We solved our nGUI issue by using a scaling script that was posted in the forums, which simply scales the nGUI assets based on a set width and height.

The problem is with particles. These do not scale, and instead show their size based off of their distance to the camera. We noticed this when we had a particle emitting behind a UI element as a border. When nGUI scales the object up to fit the 2:3 resolution, you see less of the particle (as the nGUI object takes up more screen space).

I'm curious if there are any known solutions for scaling particles based off of the screen's resolution. As we move to android, creating different particles systems for each possible resolution multiplies our work. Using the nGUI solution of scaling the graphics in runtime seems like it would be a bit too heavy to do so on particles. I've considered using a separate camera and adjusting its position based on the screen's aspect ratio, but I wanted to see if there were any good suggestions here first.

tl;dr: What's a good way to scale particles in real time without moving the camera's position?