Inside an encrypted drive,can TB standard replace TB portable? (plus other questions)

Hi,
I've been using Truecrypt for some years,and inside the encrypted drive (which is just a 2gb file stored on an external USB drive) I manage as "portable apps" Eudora Pro, Palm Desktop and Oxygen Nokia Phone Manager.
I have all my emails sent/received since 1996, for all my 14 accounts.

Now I'd like to move to Thunderbird, since Eudora is not reliable and I have problems in character encoding.
I could wait the next release of Eudora which should be based on Thunderbird, but I'd like to start moving to new mailbox format now.

I'm trying Thunderbird portable, however, since my drive letter never change (because TB is installed within an encrypted drive with truecrypt, so i choose the letter when I mount the volume) maybe I don't really need TB portable: could I install standard TB in the truecrypt volume and change in some way its ini file so that it always looks for profile data in the path I provide?

I'm actually trying TB portable v.1.5.0.8 as I found on this website, however it always ask me to download and upgrade to version 1.5.0.9; should I do it? I mean,isn't v.1.5.0.9 the standard TB? I feel that to upgrade TB portable, I should wait for a specific new version on this website, is it correct?

Some parts of TB are really poor compared to Eudora, especially the search functions, the filters managements and the handling of mailing list (=multiple addresses stored as single one), do you know if there is a way to enter the list address and having it immediately converted into the addresses it it made of? Do you think that in future release of TB such parts will be improved? (or, even better, if Eudora code becomes open source, do you think TB can make use of it?)

Thank you for your time.
/Paolo