Limitations of UME Custom Attribute mechanism

NW 7.0

For an enterprise portal UME is positioned as the way to access user data. Could someone please explain some of the limitations on custom attributes:

The apparent limit of 10 multi-valued attributes. I know that user profile is not intended

hold everything but 10 seems like a low and arbitrary number for enterprise portal

situations. Is this really the limit or is there some way around this limit.

How does the UME process IUser.getAttribute() String[]. When does the loading of

the data occur and is this configurable? Is the data all loaded when the user logs in

or upon invoking getAttribute()?

For a situation where the user might have a list thousands of items that are potentially

selected as preferences. What is the best way to access this via the UME?

Is the attribute mapping to LDAP available in Dual Stack where UME is primary data

source?