[Bug] Permanent FTP ACCESS to USB HDDs

[AlramEast]

Ok, so I followed this guide I found a few months back where I edited the 'ftpserver.sh' file by adding the following lines:

cd /etc
/mnt/syb8634/bin/pure-pw usermod ftpuser -D /opt/sybhttpd/localhost.drives/ -f pureftpd.passwd
/mnt/syb8634/bin/pure-pw mkdb pureftpd.pdb -f pureftpd.passwd

Now the problem is that I can read from my USB HDDs but I can't write to them using FTP. There seems to be a 'permission denied' some how.

Any ideas on how to get around this?

[AlramEast]

So I tried rolling back to original configuration and instead I created two folders in my /share/ .
/USB_DRIVE_A-1/
/USB_DRIVE_B-1/

I also mounted my USB-HDDs using the following lines:
mount USB_DRIVE_A-1/ /share/USB_DRIVE_A-1/
mount USB_DRIVE_B-1/ /share/USB_DRIVE_B-1/

This grants me access to read from the HDDs over FTP and write small files, but as I try to write larger files I get errors. Why?