There was never a problem with 300Bs in the Paramount. There was an issue with a few specific 2A3 tubes (the circuitry is different). The "soft-start" board upgrade (incorporated into the kit with version 1.1, in 2011) was developed specifically to address an issue at startup, which was seen most severely by the EML and one or two other 2A3s.
The other issue is that EML specifies +/-4% for filament voltage, but power line voltages can vary +/-10% (sometimes more outside the US). Never fear, we have ways to adjust that voltage if necessary. You might check your power line before you start the actual assembly.