Doing more thinking on the superconducting magrid feedthrough. Rather than have a bend between the magrid and a centered feedthrough, it would probably be easier to make a custom conflat blank with an off center 2.75″ pass though welded on. Like this:
The part would looks something like this (via MDC):
Prometheus Fusion Perfection 
Watched your plasma video… Having tinkered with this kinda stuff for a couple of years it seems the plasma instability you see in the video (changing size etc) may be due to lack of ballast from the power supply. Try some resistors in series on the HV line or some inductance. This should make it more stable and be kinder to your power supply. Good work, I follow with interest. Dustin
I also noticed little star bursts all along the inner grid. I’m assuming these are residue on the grid burning up.
As the plasma pulsated so did the voltage and current reading on the power supply.
Thanks for the suggestion. For the other readers, here is some background on ballast:
http://en.wikipedia.org/wiki/Electrical_ballast
This is normal and usually dissappears after 15mins to 1 hour.. it is due to sharp irregularities in the grid on a very small scale. It will get cleaned off smooth by plasma ion collisions with the grid. The flare coming out is due to electrons escaping through the largest hole and on very symetrical grids the plume jumps between openings. As vacuum and voltage increase it canges to look like beams through all the hole centres. There is lots of background info on the fusor forums.
http://www.fusor.net/board/index.php?site=fusor&bn=
Dustin
The ballast resistor or inductor will save your power supply from over current surges and make the plasma much more stable. Arcs can happen between the grids that can destroy your supply so its well worth looking into this. You have a cool set of equipment there and I look in envy.
Dustin
High voltage resistors:
Click to access high_voltage_resistors_90_100_200.pdf