What is the maximum anonimity set of a CoinJoin transaction? I found the only limiting factor is the maximum standard transaction size which is 100k bytes.
The most common transactions we are concerned with are 1 input, 2 outputs and the second most common are be 2 inputs 2 outputs transactions and the sizes of these transactions are about 220 byte and 360 byte.
therefore the maximum achievable anonimity set would go from 270 to 450 (100k/360=270, 100k/220=450).  


Am I correct so far?  
Is there any more limiting factors?  
Does SegWit elevate the size of the signature out of the calculation of maximum standard transaction size, therefore resulting around 30% more anonimity sets? (Signatures are 71 bytes on average.) So in this case 351 to 468.
Regardless of the maximum size of a single transaction, a CJ anonymity set can be made arbitrarily large (bounded, of course, by participants) by building a multi-stage switching network out of joins.

This was described in the original coinjoin post:


  In particular, if you can build transactions with m participants per transaction you can create a sequence of m*3 transactions which form a three-stage switching network that permits any of m^2 final outputs to have come from any of m^2 original inputs (e.g. using three stages of 32 transactions with 32 inputs each 1024 users can be joined with a total of 96 transactions).  This allows the anonymity set to be any size, limited only by participation.


There is no atomiticy required between these transactions-- other than if some users drop out the anonymity set will be less than expected.