Aerozine BB solutions are durable and well made in my experience (not saying they're Chris King quality, but they're decent). I've been running a couple of external BSA to BB30 conversion cups for over 3 years now. The original bearings it brought were crap straight out the box, but for $21 shipped while also sporting the proprietary BB wrench it was well worth the money.
Once some Japanese bearings were thrown in, the darn thing has been spinning awesome (with regular regreasing 3-4 times a year) since it was assembled. Also, the dimensions were bang-on. I merely had to take away the play adjust assembly from the frank's axle and it all fitted in the first try.