I'm about 99% sure that ECC99 does not have the same pinout as 6N6P. ECC99 and E182CC both have the dual voltage heater. The 6N6P only has 6.3V heater.
Thus the ECC99 and E182CC have 3 heater pins, one for either end and a center tap. If wired in parallel, they are 6.3C, if series then 12. Please do not just plug in ECC99 to your Val!
The 6N6P tubes use that extra pin for a grounded screen between the two triodes.
Thanks for the advice! I trust you more then that website. So would those modded socket savers work for the ECC99/12BH7 like the E182CC/7119's. In other words wire the voltage in parallel (6.3V) not series (12V). Yes 6Volt heaters don't like to supply 12V's - they tend to complain with smoke and sparks! LOL!