Can you do a clear lens mod in the stock DC4 projector? Like take another 3" clear lens and swap them? Will it make a difference?

 

Make a difference, yes.
Improve lighting, possibly, but probably not.

The optics of a projector are a combination of the bowl (reflector) and lens. Change one, and you change the optics of the entire system. The distance from the bulb, curvature of lens face, and thickness of the lens, all affect the focal point and beam width and dispersion pattern.

Now, the real question, why change the lens by itself? If you want a clear lens projector, it would be best to swap in a complete projector with the desired lens.

 

Ok thanks I was just curious. I wanted to do the fx-r projector retrofit.