you will need to build a new power supply for the heaters, the 6088 needs a 'battery' supply of 1.2v and the sort of tubes you are talking about are 6.3 / 12.6v and need vastly different currents. You will need a new high voltage supply to operate these 9 pin tubes as the voltage and bias aren't close for your tube. You will need to add some physical sockets also from the 5 pins the 6088 uses to a nine pin socket for the tube you suggest. You are basically talking a new amp but if you are going down that route try one of these for a starters.
it will allow you to mount a socket of your choice and run the flying leads to the Vali and other leads from your separate PSUs. and I thought the LD DIYs had gone weird in their mods :) at least their amp was designed to roll even if some of the tubes rolled now need serious adapters / PSUs / DIY.
I see. Well, thanks for that, I didn't know it would be that involved. Doesn't seem worth the trouble.
It's good to know that those PC boards exist though, that surely would have come in handy.