Finally got around to it day before yesterday. I am 55 kg, two others are 100 kg and ~70 kg, all capped 50 mg and had a GREAT time. Went out to dance, comeup took 1-1.5 hours, no nausea or GI distress aside from the usual "need to take a moment to deeply exhale a few times." By far the best music enhancer, better than MDMA, floaty descent, no urge to redose.
I would probably rate 6-APB the PERFECT festival/afterparty drug and dose at like, 4 or 5 PM. For "regular" nights that don't get going until late, your chances of sleeping are slim to nil.