All shapes can be made, this was simply done with a mill bit with a rond tip.There is enough pressure build up to put a lot in the channels., now it is 8mm in diameter and 4mm deep, I can use a 10mm one and still go 4mm deep, that will giv a wider opening. But I must also prevent not to take a lot of material from the backplate to hold a high pressure. I have plans to make a lexan version, just to ee if the fow is shown.