[Dovecot] Dovecot's maildir format / is rm safe

[ian at comtek.co.uk]

Is it considered 'safe' to delete directly from a dovecot Maildir? I 
mean things of the form:

    rm Maildir/cur/1288062016.M581217P9422.alpha,S=1873,W=1900:2,S

The wiki tells me 'If you wish to modify them in any way, create a new 
message instead and expunge the old one. ' but it doesn't mention 
deleted files.

Specifically I'm wondering what happens with:
    dovecot.index
    dovecot.index.cache
    dovecot.index.log
    dovecot-uidlist

Since (http://wiki.dovecot.org/IndexFiles) tells me these files index 
each message is there a chance of Dovecot breaking badly if it can't 
find them? Is it intelligent enough to automatically update the above 
files when it finds a missing message file? Would simply deleting the 4 
files be appropriate?

I have users with 4 gig mailboxes so I really wouldn't want to be 
deleting those files in a script every night if its a long winded 
process to regenerate them.

Thanks in advance for any help,

Ian