Yeah, space is very important for me, I barely have any here =)
BTW I am trying to setup a 4GB HDF in UAE as you said... but HDToolBox does not detect any hard drive.
I did this in WinUAE:
0. Load WinUAE as administrator
1. Add Hardfile
2. 4000MB
3. Selected OFS/FFS/RDB
4. Enabled RDB mode
5. IDE0 as HD Controller
6. Boot from floppy (WB3.1 install)
7. Launch HDTOOLBOX -> nothing detected

What's broken? Thanks!