removing quota files / diskconfig

hello Admin Wizards,

Machine: DEC Alpha 1000/5-333; 2 node failover cluster w/ external 
raidshelf 2xHSZ40 in SW300
OS: True64 4.0g / AdvFS

Now that the time comes that our old server is to be replaced within the 
next months, I have encountered a problem maybe familiar to you:

the /usr partition - once upon a time big enough with 1 GB - is 100 % 
full by now.

Since the server is just running for some services and compatibility 
reasons and there is no more shared filespace on the machine, I have 
thought about deactivating quota.

If I choose to do this, do I have to remove the quota.group and 
quota.user files by hand?

and using diskconfig I realized that the guy who has set up the machine 
some 10 years ago did not use all available disk space - there is som 
100 MB unused space (unpartitioned, however) lying around.
The 2 GB RZ28M shows partitions as follows:
a: boot 0-128.000
b: swap 128.000 - 847.929
g: usr  847.930-1871.929
unused: 1817.930-2007,070
thus free: 135.143
a small portion, but it would help over the next months.

Can I make this waste space useful with the machine up and running? I 
use AdvFS as file system.

thanks for every hint
CW