You need to have cuminside over 500 ml.If i remember correctly it will have 4 stage of cumflation.It should be 500 1000 1500 and 3000ml but after 1000ml cum will leak really fast.If you want to see 1500 and 3000ml version you need to use bug that i tell in my edit comment.I think next update body system maybe have way to increase max amount of cuminside you can have.