I have an HC-1 but was thinking about getting the Sennheiser Evo wireless lav setup. The receiver comes with a cable that plugs into a 3.5mm jack on the receiver and gives an XLR jack to plug into your camera/sound system.

However, I was wondering if I could get a cable with 3.5mm stereo connections on both ends and plug it into the receiver and then into the camera body. Would this work?

The goal for all of this is to add as little extra weight to the camera. I don't want to have to carry a beachtek or (ideally) a big XLR to 3.5mm adapter.

Simply, yes - this should give you the audio on both channels. I use the same setup with a lectrosonics 100 rig and it is great.