opinions on my center pin set up

I do not believe that you need to use 10 and 20lb premium fluoro at all. I would go with cheaper P-line or sonething similar.

I just do not think you need premium fluoro for your backing. I would rather put on some soft mono like Seaguar Senshi or P-Line. I would go 8lb with 20 backing.

Thank you very much

For backing I found a spool of 18 pound test Dacron? line made for ice fishing in a junk box at a yard sale.  I've had this on as backing for a couple of years now and I still haven't seen the line in use while fishing.  I'd use whatever you can find on sale.  Maybe even something like fly line backing or even one of the brands of braided line.  The main reason I used what I did was the line has no memory and doesn't take a set like mono does.
 
My running line is 12 pound siglon F but anything from 8 to 15 or so should work.  As suggested I would try to find something that floats as long as it isn't a braided line.  The braided lines will soak up water and freeze faster when winter steelhead fishing.

I saw p-line has a floating line. Is it good?

Go cheap on the line I if you never pinned you will tangle most of your line probably cutting off 10% or more before you get the hang of the casting.  A pin is fun on big water, I take it up to New York and fish browns with it.