VirtualBox Guest Shared Folder Ignoring umask

I have a folder on my host system (Arch Linux) which is being shared with an Ubuntu VirtualBox guest. Instead of using automount, I am mounting the folder at boot using the following line in my guest's fstab file:
sharedfolder /var/sharedfolder vboxsf rw,exec,uid=root,gid=mods,umask=0002 0 0

The folder is being mounted successfully, and with the proper owner and group, but the permissions are being shown as missing the w permission for the group. The relevant output of ls -lh is below:
drwxr-xr-x 1 root mods 4.0K Jun 1 16:41 sharedfolder
whereas I want it to be:
drwxrwxr-x 1 root mods 4.0K Jun 1 16:41 sharedfolder

I specifically need any user belonging to the group mods to have full permissions in this folder, which is currently not happening.

I have tried using chmod 775 sharedfolder, but the permissions do not change, even when ruing the command with sudo.

Any advice would be most appreciated.