I can back 5.  to back 3, you almost bounce sideways( I do anyways) throw your arms about 11 o clock and spin BEFORE you flip.  If you try to spin first, THEN flip you can spin a hella lot more. back 180 look like crap if you do em wrong which, if you can't do a back 3, yours prolly do.  They look much better if you spin AS you flip, not after the flip.
I Lays It DOWN for ya