So you think that your liquidity is high enough to beat the exchange price even with your "premium"?
Such large trades that they will get a better deal at your premium as opposed to the slippage they would encounter at an exchange on top of spot rate?

How much premium % are you talking?
I would like to know so I can go calculate how much BTC would have to be traded with a market order in one slam to make your premium the better deal, because slippage..