The IPL can scan the entire combined image for the presence of the startup header, but this slows the boot process. Instead, you can have the IPL scan through a range of only two addresses and place the startup header at the first address.
Specifying a final IPL size that's larger than the actual IPL lets you modify the IPL (and change its length) without having to modify the scanning addresses with each change. This way, the starting address of the OS image is independent of the IPL size.
Padding before .ifs images
If your combined image includes one or more .efs images, specify an alignment equal to the block size of your system's onboard flash. The optimized design of the flash filesystem driver requires that all .efs images begin at a block boundary. When you build your combined image, the IDE adds padding to align the beginning of the .efs image(s) with the address of the next block boundary.