When you use the 'Convert Stereo to Mono' option on a clip, it just adds the left and right channels, so depending on the levels you can end up with the sound clipping.  Is there a way to change the way it mixes it down to use 50% of each channel so you're guaranteed not to get any clipping?  It's a pain in the ass having to move it out to Sound Forge to do a seemingly simple operation so if there's a way to do it you'd save me a lot of time.  Thanks!

One way would be to bounce the track to a new track and select the new track format as Mono.  The test I just did does not appear to produce any clipping.

Or use Process -> Audio -> Gain to lower the track 3db before folding to mono.

i am trying to do this right now & when i convert to mono from a stereo master (for youtube video play on mono phones), there is missing audio in the mono mixdown that is present in the initial stereo version.  this process makes some of my guitar solos disappear!  is there a step to this process that isn't listed here?

Sounds like you have a phase difference between the left and right side on some sounds, maybe a wide chorus or the Haas effect? I don't know of any way to fix this outside of the mixing stage.