Hello Greg,
I haven't implemented it in anger, but I'd like to clear up the agent versioning, at least try to clear things up..
We would say to use 10.2 legacy agent as it would be the last version of the agent that would supply the WebSphere Portal monitoring out-of-the-box. That version of the extension to monitor WAS Portal was not updated to agent new mode.
The extension you get from CA Marketplace is a port of the extension to new mode, as the description on marketplace says:
"Migration of product version of PowerPack for WebSphere Portal to HC (agent new mode) version. No features added or removed."
That marketplace version could therefore be used with the normal agent, no reason it could not be used with 10.5 but it won't have been worked on with Team Center in mind for example.
We should also state the updated extension is not supported by support itself, whereas I would have to be honest and suggest the 10.2 legacy extension should still be supported by support.
All I remember from the implementation is you need to put pbd/pbls in the core/config folder and specify in the agent profile, and add the agent jar file to the /core/ext folder.
A while ago, it used to be necessary to copy the agent extension jarfile to the /shared/app folder (or similar name) into the WAS Portal install itself, but that requirement was removed in any option that is currently available.
According to the 10.2 compatibility guide, it does support Portal 8.5.
The other question could be about support for release 10.2, all I can say is we still list support for 9.7 so I'd like to anticipate there would still be a few years before 10.2 is out of support.
Thanks,
David