I decided to go with a heavier line for pitchin my plastics and right now I use a Core reel, and instead of braid, I went with 20lb fluoro.  Maybe I spooled too much on the reel, seeing how its rated for 90yd of 12lb, I filled it till about 1/8-1/4 from the outer spool.  Anyways, it works but when reeling in and such the reel doesnt reel as smooth, is 20lb too big for this smaller reel?

Too thick.

Either go to braid or try what I use: #12 Yo-Zuri Hybrid

(.013" diameter, 19.5 lb breaking strength).

8-)

The reel is not "rated" for 12# line, it just indicates how much line of the common 12# diameter mono it will hold. You can use whatever your line choice may be and may range from 10 feet of weedeater cord to 200 yards of 2# mono. In the same brand of monos/fluoros, the heaver pound tests are stiffer than the lighter pound tests. How it reels in is affected by drag on the line guides if the reel worked OK before using the 20#. In most cases, the fluorocarbon has less rod guide friction than nylon monos or co-polymers.

# 20 is pretty thick...  the only way I could see using line that heavy is by replacing the spool...

http://www.bassresource.com/bass_fishing_forums/YaBB.pl?num=1244408845

it works fine for short line apps, such as pitching, flipping, etc....but, for longer line apps (cranking, spinners and c-rigs, etc.), you can run outta line pretty quick...depending on rod and thumb.

the 12# yo-zuri hybrid mentioned above is my recommendation, as well...it is a strong, tough line that works extremely well on the core.