Green’s Dictionary of Slang

beamy adj.2

[off (the) beam under beam n.3 ]

(US black) wonderful, a play on crazy adj. (2) [on bad = good model].

[US]L. Durst Jives of Dr. Hepcat (1989) 2: Great and much straight and everything is tight even ‘Charlie Chan’ would have to come to land. And everything is much beamy.