I am using BBMPEG to multiplex, and using the multiplexing start/stop/size options to create 2 MPGs to burn to 80 min CD.
Starting with an 4 pass VBR MPV that is 1,427,410 KB and the audio MP2 is 148,812 KB

Total time of the movie is supposed to be 105 min 51 secs = 6351 secs
Half of this is 3176 secs

So, I use the start stop settings in BBMPEG
First CD = 1 to 3176 -> Creates MPG that is 792 MB
Second CD = 3177 -> 6351 CREATES MPG that is 819 MB!!!

Why the larger size for the second split?? I ended up just burning to SVCD anyway, and it just cuts off in the credits, so not a big deal, but I really want to get this process figured out to avoid this happening again.
It just occured to me though that since I used VBR to encode the movie, there might be more "bits" associated with the second half, and hence the larger file size - would that explain it? In which case it makes since to do the 2 separate CCE encodes on each half if you are trying to keep to specific size?