Hello all! I've been smoking for a while, but am new to the bong area of smoking. I'm about to build my own bong and am worried about compatability issues. Could you guys please tell me if these would work together? I'm also wondering what size hole should I drill into the glass to fit this downstem, since there is no specification. 5/8? Downstem - http://420armory.com/main/index.php/funnels/glass/two-piece/tubes/18-top-18-bottom-2-5-inch-204-205-206-207-208-detail Bowl - http://420armory.com/main/index.php/funnels/glass/two-piece/tips/honey-pot-18mm-funnel-tip-detail With this downstem, I don't need a grommet correct? Thanks for the help guys.