Thank you for your question.
You wouldn't need a balanced flue for the Eko Fires 6010 stove as it is a flueless model and uses a catalytic convertor to clean and purify the exhaust gases.
In order to use the Eko 6010 stove you will have to cover the vent as any draught from the vent may cause the built-in safety ODS to operate incorrectly.
I have emailed you a copy of the installation & user manual to give you a fuller picture.
Hope this helps?