The 12 bolt can be built into a great assembly with the only potential issue being the axle retention. I would recommend having the housing end replaced with with an end that accepts a large Ford/Olds style 3.150"O.D. bearing or a floater assembly. There are C-clip Eliminator kits available but you will need to be sure to use one that has a tapered bearing vs the low friction ball bearing type. You've got alot to consider but it seems your getting some good information here.

Wil.

I have seen problems with knock back with both the Set 20 tapered bearings & the ball bearings. Currently I'm favoring the ball bearing slightly. The last rear we used I let Currie talk me into the Set 20 tapered bearing ends & we are not happy with them. The One Lap Camaro had the ball bearings & less knock back but did have a bearing failure.

So if building a 12 bolt (narrowing, buying axles and bearings) which setup is the best? Or do you just have to accept bearing failure, leaks and pad knock back? Is Going full floater the only real solution? But maybe it just depends more on the weight of the car, offset of the wheels and how hard its actually driven on and off the track as to how much problems you actually have.

When we make recommendations for axles, bearings and Diffs. we take all of the factors you listed into account.
Much like your suspension you will need to clearly outline the intended use of the car. Build the 12 bolt and enjoy the car. When things get more aggresive and the car is spending more time setting great lap times start to consider your options, floater assembly with new axles for the 12 bolt or a completely new 9" with a floater. Whatever you chose consider future proofing yourself.
Wil.