Those aren't 'plate burners' - they are low-end exposure units for printed circuit boards and for DIY labels. The double sided one is for double sided printed circuit boards.
They are not a good choice for your purpose.
- Liquid Light is not a UV emulsion.
- They have poor contact pressure.
- The light is uncollimated.
Use a standard spring back contacting frame and a small light bulb hanging about 3 feet above the frame.
A plate burner will have a vacuum blanket to clamp the materials together and the light source will be a mercury vapor or HID lamp that is several feet from the frame. The smallest are about the size of a washing machine. There are also overhead units with the light above the contacting frame and a curtain that pulls around to shield you from the light.
There are boxes that are similar to plate burners made for exposing silk screens. The blanket system is not designed for flat a/w but for silk screen frames. Some of these units use banks of flourescent bulbs.