This chassis has a very large HV door knob cap mounted to the back side of the HV cage. On my set that door knob was bad, probably leaking. I purchased a 40KV replacement on ebay. I needed to modify some of the mounting hardware, but it works fine.
I would suggest that you check the big 30KV door knob to see if it is getting warm which would indicate leaking. If yours is leaking, I would replace it before it wipes out your flyback.
I also installed a small cooling fan in the side of my HV cage to keep my flyback temp nice and cool.
When I restored my CT55, I placed the cabinet next to my workbench and made extension cables to connect the chassis to the crt and other components in the cabinet.. That worked very well.
You may find this link to the page on my web site of some use.
http://antiquetvguy.com/WebPages/The...CA-21CT55.html