Or just a few screws and the chassis comes out for easy access.
You may not plan to make individual adjust controls - and I myself think that would be overkill - but really, add the 1 ohm resistors to all four sockets, even if you only bring one to the panel. It will give you current reading access for troubleshooting later in life. And resistors are cheap.
My personal choice would be pin jacks rather than banana. A pin jack takes your probe point. My concern is that you want a jack that has no chance comeone can touch it with a finger, and is not readily poked my anything conductive. That is going to be 400-500 volts, which is lethal. Or thinking about it, maybe a terminal strip behind a rectangular chassis hole, and a screw-on cover plate. Then you remove the cover plate, and can probe all four points, well five including your tube plate.
One could have four test points brought out to one jack with a four way selector switch next to it.
I personaly am not comfortable with plate voltage on a test point, but I am sure many guys do it. All it takes is one moron with a paper clip sticking it in ther thinking "Oh these test points only have a few millivolts..." Help, I've fallen, and I can't get up.
As far as the amp is concerned, test points don;t exist, so add them as you like. I explained my thoughts on it, but none of the arrangements affect performance, so one post or four, go ahead.