Multiple Tempo Maps Problem

[hef]

I'm trying to combine multiple tempo maps into a session where the audio is locked to timecode (29.97 dropframe). Basically, I get the music in stages, 1 act at a time and would like to bring in the tempo maps with the music. Each acts tempo map is fine in its own session and lines up perfectly with the grid and timecode. When I combine them in one session that's when things get screwy. Here's how I've been combining them:

I have act 1's tempos map in and lined up fine. Then I import the tempo map for Act 2 and it blows out and erases act 1's tempo map . Then the only way I believe to remedy this (saw a thread in the DUC) is to import Act 2's tempo map (the grid and tempo map are fine for act 2 as of now), then copy Act 2's tempo map, then import act 1's tempo map and then paste Act 2's tempo map. After doing this Act 1's tempo map is fine but act 2's is slightly off the grid. Act 2's tempo map is exactly where it should be as far as timecode and audio but the grid is off. The first tempo change marker is right on the first beat/clip of audio, however the grid is slightly off. Each of these tempo maps and grids are perfect when opened up in their own session, its just when combining them the grid is off for the 2nd tempo map. any way to fix this without moving the audio??