Turns out it was super simple. Setup your storage, add a backup to the storage. Once the backup is created you can click the - under the Options column as highlighted below and enter the Command Options as per my image
-threads 8 -limit-rate 8680
After making this change I can now upload at around 5MB/s so over double what I was seeing before. I suspect the thread limit is CPU dependant so 8 is my limit speeds not to bad for 200GB I need to backup on initial seed.
Thanks all sorry for any trouble caused, seems it was simple in the end.