Presetting the root size not working CONFIG_TARGET_ROOTFS_PARTSIZE

I am attempting to set the root image size.

In my .config, I have the following:

CONFIG_TARGET_ROOTFS_PARTSIZE=750

This replaced the 105MB size (I believe) that was originally in there.

Even doing a make clean doesn't seem to fix the issue. I've even gone to the extreme and manually rm -rf bin/ build_dir/ and then a build to no avail.

The output file I'm using is openwrt-octeon-itusrouter-ext4-sysupgrade.tar.gz
and exploded on the device in /tmp:

root@Shield:/tmp/sysupgrade-itus# ls -la
drwxr-xr-x    2 root     root           100 Jun 27 05:12 .
drwxrwxrwt   18 root     root           500 Jun 27 05:12 ..
-rw-r--r--    1 root     root            11 Jun 16 06:35 CONTROL
-rwxr-xr-x    1 root     root       9184024 Jun 16 06:35 kernel
-rw-r--r--    1 root     root     109051904 Jun 16 06:35 root
root@Shield:/tmp/sysupgrade-itus# 

The ```root`` refuses to expand to the 750MB I'm asking for.

Any idea what I'm doing wrong?