stereo to mono producing clipping

I know this is a rank amateur situation, but that's me.  I recorded some vocal clips in stereo without setting levels carefully (or accounting for the vocalist getting more dramatic with the handheld mike during actual takes than during the check).    Realizing that the clips oughta be in mono, I converted them, but this produced clipping on some of the stronger syllables, where there was none in the stereo version.  I guess this is because the algorithm is adding L & R together (but not linearly, right?, because it's not like the volume simply doubles)?

Is there a surefire way to tell before hand whether the stereo to mono conversion will clip any portion of the recording?  Does the track interleave setting affect the stereo to mono conversion?  (Using X1c x64, latest patch, under Win7x64.)

Incidentally, panning the converted mono clip full left or right still leaves sound in the other channel (even though the meter indicates there's none), but I don't have enough experience to determine whether this is a panning bug (reported by others on this forum) or there's a panning consideration associated with converting from stereo to mono that I simply don't understand.  I have multiple clips on a single track, some still stereo some converted to mono.

Thx,  Ron

Thank you James.  So the pan laws do affect stereo to mono amplitude conversion - that's good to know.  I may have caused my first problem by trying to address the panning issue I also mentioned.  Although I think I'd done the stereo to mono conversion before changing the panning law, not sure.

But yes, (I neglected to say) I had changed the pan law from the default (-3db etc.) to the 0db you mention when trying to solve the panning issue mentioned in my last paragraph.  That issue is not solved by changing pan laws, but I've now shown that after moving the clips to a new audio track, panning works properly for both the stereo and mono clips.  I found a thread a couple weeks ago where someone reported the same thing.  So there may be some sort of panning issue associated with an occasional audio track. 

Understood various factors can cause unexpected pan results.  (I did check my sound card and external mixers etc. before posting.)  Don't think it was anything but a track issue (bug?) in this case.  Won't worry about it til after X1c.  For the moment, two problems solved - thanks again!  -Ron

I would advise caution before altering your pan law mid-project, as it will throw off all your pan settings and may require you to remix everything.

But James is right in suggesting that it's the summing of two identical signals that results in the increase. That's why pan laws exist, to automatically compensate for this effect as you move tracks across the panorama. Setting your pan law to -3db is handy if you use pan automation, so that as a track moves to the center it doesn't get louder. Personally, I prefer the 0db law (no compensation), but everybody has their own preference which is why there are multiple options.

The solution to your immediate problem, however, is easy: lower the volume on your track, either before or after converting to mono. If it was that close to 0db to begin with, you're recording too hot. You'll want to leave more headroom in the future.