Homemade Bong Help

im trying to make a bong and i wanna kno how should the bowl go in and i kno every bong is different but where is the sweet spot i guess is what im trying to say or how should it look

just make a third lung, best working homemade bongs imo
easy to make, and its always free, if you buy 2L's of any beverage

It should look something like this;

i like em low so that theres more room for smoke + no splash/sloppy bubbles. but anything will do