@countzero:
I think the problem is as simple as in 1.3 chip-memory per default had higher priority than fastmem (to aid in compability with som poorly written software and hence the reason for existance of the utility FastMemFirst) and because of that everything will be loaded info chipmem first. So try loading FastMemFirst very early in your S:Startup-Sequence and see if it makes a difference.
Don't worry about the single ground. First of all, the ground for power is the same, disgregarding if it is for 12V or 5V and second the two ground-pins are connected to eachother in the harddrive. Nevertheless it is imho a bit cheapskating and poor to just give the cable a single ground line.
/Patrik
