I'm not sure why you're combining them and then splitting again. I'd split first, then just join the two files that are on the boundary between 2GB files. In other words, if file A contains tracks 1, 2, 3 and part of track 4, while file B contains the rest of track 4 plus tracks 5, 6 and 7, then just split A into 1, 2, 3 and 4a. Split B into 4b, 5, 6 and 7. Then just join 4a and 4b with the editor of your choice.