I am looking to buy my first centrepin and I am confused over the differences, ie width and diameter. Are certain specifications better for certain conditions? Are some better for ledgering and others for trotting? Do you load the line so it spools off from the top or bottom of the reel, or is it a personal choice?
width: narrow spooled reel are generally not so good for ledgering because of lines bedding in ,when using heavy ledgers ,whereas a wide spooled one the line is spread more evenly .and resists bedding in
but for trotting ,it doesn't really matter ,but the wider spooled reel might give you less chance of bedding in ,after catching a big fish ,but asthetically its personal choice
there is another consideration in that a full faced drum (flat bottom) is better than a pillered (pins) aerial type ,which can cause crimpling of the line (comes off the spool ina zigzag fasion) ,and it gets a memory of the angles between the pillers .wareas a flat faced spool doesn't .
diameter : Dia = retrieval rate .in general the larger the dia the more line you wound back onto the spool with each turn . but there are exceptions some reels have a deeper arbor than the dia betrays .thereby the diametre of the spool isn't the reel factor ,the Radius of the drum is ,case in point a 4" (spool dia) speedia has a drum diametre of about 3" across the pins .wether its a wide or narrow spool .
reel sizes :are a personal choice ,but in general a 4"-4½" is a comfortable size for most hands .I prefer too match my reels (well all my tackle) too the venue inm fishing ,so on big rivers i use big centrepins (4½" - 6") and medium sized rivers or still water i prefer reels around the 4" mark and on small rivers i prefer 3½"-4" centrepins.but basically its what your comfortable with .if limited too one centrepin then i'd recommend a 4"-4½" centrepin as thats the best compromise range.
Line exiting bottom or top: line comming off the bottom means you wind the spool in a conventional (as with open face reels) manner and is more flexable with casting options .whereas with the line comming off the top might have some precieved advantage when trotting , never found that too be the case myself ,maybe 100 years ago when reels was a lot less free running than modern reels are now.It also has limitations too casting options and you wind in the line backwards too the conventional manner.
but you have too try both too find which suites you
i hope that helps