I think the carbon fiber tri oval will fill the space left by the stock exhaust.
I would like to actually see how it looks on some other guinea pig's 300.
A pic would be valuable. I trust that the sound will be fine.
From what I read and observed, the 8" is a monster and barely legal, but the 9" ds70 is not quite as savage and a bit lower db level. There is a difference especially in the exhaust opening. Go to ebay and search for the product: "delkevic exhaust ninja 300". You can contact the company seller and ask them questions.
Delkevic is wildly popular with Suzuki SV650 riders but hasn't caught on with other bikes. They seem to make a quality product but their business model (marketing) is underwhelming.