I think the problem loading the Hex is down to a problem with the basic Hex loader which doesn’t seem to like short or overlapping hex records. The build for Alterbios and Pawn seem to prodcue a couple of instances of these probably as segment changes are made. My theory is that the buffer used to hold the hex data is not cleared out properly prior to each record but I have never managed to find the source for the base DFU to verify and or correct any problems in this area. I have successfully loaded problematic Hex files by manually combining the couple of short records that can occur in Pawn / Alterbios. I would not rely on apps where it doesn’t complete loading successfully as part of the file near the end may not have flashed properly.
On the version of which SYS is used the main difference between the one for the 2.72 and earlier versions is the support for 8MB flash, but ALTERBIOS replaces these routines anyway so it should not matter which you start from.