I know this is a stupid question but I’m curious about running some 20lb fluoro on a zillion. I never, like never use straight fluoro or mono, I can’t tell you the last time I spooled a reel with anything but braid. Im considering throwing some 20lb on a zillion. Will 20 pound be way too big for a smaller reel like that? I’m picturing using it for chatterbaits.

You might struggle with capacity. I have 17# elite mono on mine. It is 0.016” diameter.  I’ve got about 55-60 yards on it. Elite is pretty thick.  If you’re using something like sniper where 20# is 0.0146” then you’ll be fine. If you’re thinking big game fluoro at 0.019” then you won’t get enough line on. 
 

That said, I’d question why you’re looking at 20# line for chatterbaits. Maybe you have something specific in mind, but for most applications that’s a lot heavier than you need. Something in the .013” range is a solid choice. The thinner line will let the bait run deeper and truer, and it will be easier to cast and manage. 

You’re good to go.

You can.  I don't like the way flouro handles in those diameters  I'd try 15 pound Big Game 1st.  It's a large diameter plastic line that will fail at over 20 lbs and will far exceed the handling of even line conditioned 20 pound fluoro.  If you hate the handling of that then fluoro is a no go. 

 

I might actually switch my high end moving bait rig from 16 pound sniper over to 15 pound low vis green Big Game after trying it on my budget rig.  For moving baits both are basically the same in visibility per diameter and the BG let's me throw buzzbaits and ploppers on that rod.

 

It's got a pretty small spool for 20lb.  17lb Tatsu or some thinner high end line might be workable.

I just put 22 Daiwa Samurai on a metanium to flip with. But unless you’re trying to run that CB thru very thick cover it’s probably not necessary.