iirc forestry frames stop boosting production rates at 1000% (4 frames will more than cap it). Frames from Thaumic Bees (Mindcrack is a 1.4 pack, so not Magic Bees yet) require vis to operate. With that many running, I wouldn't be surprised if you depleted your aura pretty severely and that cut into your productivity.
Genetic damage from overstimulated production (production chance >1600% or mutation chance >1000%) was introduced in 1.5 I think, so it shouldn't be a concern in Mindcrack. The production caps on forestry frames are still there (pretty sure - most documentation has long since been updated, so I'm running off memory at this point).
You only have a chance of producing 1 standard produce and 1 specialty produce every bee tick (every 27.5 secs). Taking the Radioactive Bee as an example: its standard produce is a barren comb (20%) and its specialty is a radioactive comb (2%). The production speed and frames then apply a percentage modifier on to that chance. For speed that ranges from 30% (slowest) to 200% (blinding, which is not available in Mindcrack). Fast speed is a 120% modifier, so you now have a 2.4% chance of producing a radioactive comb. An alveary gives you 100% of this (i.e. maintains a 2.4% chance), but an apiary will apply a 10% modifier to your production chances (brings that number down to 0.24%). Each production-enhancing frame applies a 200% modifier. 1 frame boosts that 2.4% to 4.8%, the next boosts that to 9.6%, the third hits 19.2%. The effect of the fourth frame depends on if you're using forestry frames or not. If you are, then the production boost hits its cap at 10x the non-framed production - in this case 24%. If not, you continue doubling to 38.4%. For those using packs from 1.5 or later, this is the cutoff for where bees start turning ignoble. If you keep going, your 5th frame will give you 76.8%, and your 6th will have you well over 100% to guarantee you a specialty drop every 27.5 secs. There is absolutely no reason to go beyond 6 frames, even for super low chance specialties (a 1% chance like from the diamond bee would still get over 100% with fastest production speed).
If you want 1 stack of Uranium every hour that means you need 2 stacks of Radioactive Combs/hr. There are ~131 bee ticks every hour, so you would essentially need a 100% chance (6 frames in an alveary) of producing a specialty every bee tick to reach this level of production off a single bee. 3-4 bees (depending on forestry/non-forestry frame selection) in alvearies running with 4 frames each would satisfy this production rate for people in 1.5+ packs.