To pad the file size out you would need to reverse the binary and add CPU NO OP instructions (essentially a no-op sled). roughly, you need to find the current actual size and the needed size, find cpu documentation detailing CPU op-codes, disassemble the binary, add the nop instructions till it...
No Longer an issue for me, the cost of 1TB RE 4 WD drives has fallen drastically. from the mid $400 price point to less than 200 dollars. This puts it within range of the 1001 FALS.
See:
http://www.amazon.com/Western-Digital-Cache-Enterprise-Drive/dp/B003SANWI6