By using a union rather than a struct to portably align the heap, it is possible to spare a "long" in memory, which is otherwise wasted. I have filed an enhancement request with a proposed patch to heap_1.c and heap_2.c.

Good plan – this is what I do in other projects but have shied away from using unions in FreeRTOS because they are against so many peoples coding standards.  In this case I think it is fine though as the long is there purely for alignment and never accessed. Regards.