Cannot create SW RAID??

This is the second time this has happened [on different machines], and it's a big problem as it prevents us from updating/rebuilding machines:

* When rebuilding a machine we would like to convert the HW RAID to SW RAID so it can be monitored via /proc/mdstat;

* During the installation process, it is proving *impossible* to create a new SW RAID5 or RAID6 array (RAID0 for swap does seem to work OK, so it may be related to the structure chosen?). After configuring the SW RAID, installation fails because the partitions selected for RAID5 are "BUSY"!!

We have tried:

a) Installing blank GPT tables during installation (drop to shell and return);
b) Installing blank GPT tables via Rescue System;
b) Installing blank GPT partition table on each disk via System Rescue [distro];
c) Installing blank DOS partition table via Rescue System;
d) Installing a blank GPT partition table via System Rescue;
e) Formatting the disks with NTFS;

NONE of these options allowed the Installer to build the SW RAID! The VERY FIRST install actually completed, but the system did not boot.

Are there any recommendations posted for answers to questions like:

1) What is the best partition table and boot configuration for SW RAID?
2) Why does the installer think that partitions are "busy" when the target partition table is empty?

TIA!

Lee