Western Electric or Takatsuki 300Bs?

I hope it is not the case, but, I suspect that you will have to be concerned about one tube becoming prematurely weak in your parallel SET setup.  I have not heard of any "cure" for this condition, and certainly Audio Note amps were prone to this happening.  I have a pair of Kageki parallel SET (2a3) that has this as an issue.  The thing is that the amp continues to sound very good even when one tube in a pair tests quite weak.

Good luck on your build and on your search for 3oobs.  

Companies losing billions to china and yet they keep their proprietary design data on public accessible servers (not counting on-site thieves)? These people don't sound very bright.

I decided to go with the Western Electric tubes for now. I’d like to try the Takatsukis at some point, but the WE tubes are sounding very nice. 
 

@larryi - I don’t know why I would be concerned about one tube being weaker than the other. This will cause a small reduction in peak power, but this doesn’t concern me. 

The primary concern would be whether PSET prematurely kills tubes.  I primarily ran EML 2a3s in the Kageki and a set of tubes did not last much more than two to three years or so.  I know that other amps, both SET and pushpull running these tubes tend to have longer tube life than this, but, I don't know if that to do with PSET operation vs. other aspects of how the tubes were run.  

The old WE reissue 300bs (from the early 1990s) were extraordinarily long lasting tubes; I know a number of people still running the same set for 20 years.  If the newly reissued tubes are expected to last as long, I hope that your amps will have that kind of tube life.