So i was looking on here for a solution to modify my vold.fstab folder so i could use my external sd card as internal memory and there didn't seem to be a solution for the 9 g3  that actually worked so here it is
Tried and tested 100% working.

1) download ex explorer
1.1) (optional if you have data on the internal sd you should connect it via usb and move it to your external sd card!)
2) open explorer and options set the root options so you can modify the root (tick all 4 top boxes)
3) head to the / page by going back from the sd card find the etc folder then the vold.fstab MAKE A COPY OF IT ON YOUR EXT SD CARD FOR SAFE MEASURE!
4) open vold.fstab folder
5) so to edit it now is really simple heres a example vold folder from a earlier arnova tablet but looks to be very similar in fact identical..

## Example of a standard sdcard mount for the emulator / Dream
# Mounts the first usable partition of the specified device
#dev_mount sdcard /mnt/sdcard auto /devices/platform/goldfish_mmc.0 /devices/platform/msm_sdcc.2/mmc_host/mmc1
dev_mount flash /mnt/sdcard auto /devices/virtual/mtd/mtd9/mtdblock9
dev_mount sdcard /mnt/external_sd auto /devices/platform/rk29_sdmmc.0/mmc_host/mmc0
dev_mount udisk /mnt/usb_storage auto /devices/platform/usb20_host/usb /devices/platform/usb20_otg/usb
## Example of a dual card setup
# dev_mount left_sdcard  /sdcard1  auto /devices/platform/goldfish_mmc.0 /devices/platform/msm_sdcc.2/mmc_host/mmc1
# dev_mount right_sdcard /sdcard2  auto /devices/platform/goldfish_mmc.1 /devices/platform/msm_sdcc.3/mmc_host/mmc1

## Example of specifying a specific partition for mounts
# dev_mount sdcard /sdcard 2 /devices/platform/goldfish_mmc.0 /devices/platform/msm_sdcc.2/mmc_host/mmc1

6) find this line
dev_mount flash /mnt/sdcard auto /devices/virtual/mtd/mtd9/mtdblock9
dev_mount sdcard /mnt/external_sd auto /devices/platform/rk29_sdmmc.0/mmc_host/mmc0
dev_mount udisk /mnt/usb_storage auto /devices/platform/usb20_host/usb /devices/platform/usb20_otg/usb

7) simply swap the words sdcard and external_sd around!
8) save the file! ( if this does not save then you have not done step 2 correctly opening the root! so repeat that!
9) once all that is done close explorer and reboot your arnova 9 g3!
10) presto you now have a lot more internal memory

NOW i take no responsibility if you brick your tablet! (stuck at arnova boot screen)  but fear not i done this myself the first time fortunately it was new so i simply put a pin into the reset button before i restarted the device i held the menu button and switched it on still holding menu, when it boots up wait a second to release the menu button then tap the on and volume + button repeatedly untill the system recovery comes up! simply recover the system following the onboard options and retry! it does work  thankfully!

I hope this helps! if any1 has any questions you can email me at dex1990.dh@gmail.com and ill happily help!