3cm seems like a lot. The closer the element is to the ink, the faster it will reach cure. I have a conveyor dryer, but I have used my heat press for curing. I adjust the press so that there is almost no pressure on the shirt (you can probably do that by adjusting the screws over your element). I lower the element so that it's close to the print for around 10 seconds. This dries the ink, but it doesn't cure it. Then, I press the shirt with extremely light pressure for about another 10 seconds using non-stick baking paper just to protect the plastisol. That cures the ink without making it too shiny.