There's another DIY video on youtube that is pretty much the same thing and that one is a lot more stable. He has padding on the edge of the bowl (But the bowl is way too small so the ball sits on, not in, the bowl. If you get the drill press drilled to a table and the bowl center, it should be stable. I'm thinking of getting weather stripping to line the bowl (the kind that lines your trunk). Putting weight on the drill press itself might be a problem, though, as I don't know how strong they are.
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Current Arsenal:
Siege
Evil Siege
Python
Midnight Vibe
T-Zone (Spare)
Copperhead(THS Ball)