I think the first step to learning what does and does not work and why, would be to figure out what the attitude is doing in the first place.
I have never had one, but had always thought it was merely an ICP sensor output signal modifier. Meaning, it cleverly lies to the PCM about the current level of ICP, so that the PCM will think the ICP is lower than it really is, then jack up the IPR duty cycle until it sees what it wants to see. Then you get more ICP than you have programmed into the file being run on the PCM at that moment, whether that is the stock file on the PCM's EEPROM, or a file having been flashed in place of the Ford calibration, or even a calibration being read in through the J3 port, off of a chip. Doesn't matter. In either case, the attitude is merely telling the PCM that the ICP is lower than it really is.
So, if you are running a calibration on or attached to the PCM that is calling for sub-optimal ICP, and you then crank up the attitude, you could expect a bit more power, although in reality, I wouldn't expect much over 30hp. However, if the calibration on or attached to the PCM is already optimized, and you crank up the attitude and make the PCM call for even more DC because it thinks the ICP is low, you'll get more ICP than you need, or in the case of a single stock hpop, you'll reach a disparity between ICP desired and ICP attained that will set a 1211 DTC and you will get a SES light show in the corner of your instrument cluster.
But at the end of the day, there is nothing magic that is going to make power by "stacking". If you wanted, or needed more ICP, you could have, and should have, merely called for it.
The "stack" is just a round-about, "bush-league" way of achieving the same, or similar result.