I've done this before on a couple of reels for bottom fishing. To get the fullest amount of backing without guessing you'll need two empty reels the same size or larger than the reel you're spooling. I've used this method to put 600 yard of 130# hollow spectra on top of some older 200 solid spectra.
First, empty the 100lb mono from reel #1 onto one of the other empty reels (#2) (You could also use an empty line spool and some allthread rod to make an arbor to chuck in a drill to help quickly empty the reel. I like to use a spare reel so I can spool back on with against some drag). Spool the 300 yards of spectra onto the empty reel #1. Tie the spectra to the mono on reel #2 (bimini/reverse albright) and continue filling reel number #1 until full.
Reel #1 is now full with your mono/spectra but it needs to be 'flipped' so the mono is the backing. To do this, spool from reel #1 to reel #3 (mono will be backing). Then spool from reel #3 to reel #2 (spectra will be backing), then finally from reel #2 back to reel #1.
This seems kind of cumbersom and lots of winding, but if you want to get the reel full and have the most backing under the spectra this works really well.
David
First, empty the 100lb mono from reel #1 onto one of the other empty reels (#2) (You could also use an empty line spool and some allthread rod to make an arbor to chuck in a drill to help quickly empty the reel. I like to use a spare reel so I can spool back on with against some drag). Spool the 300 yards of spectra onto the empty reel #1. Tie the spectra to the mono on reel #2 (bimini/reverse albright) and continue filling reel number #1 until full.
Reel #1 is now full with your mono/spectra but it needs to be 'flipped' so the mono is the backing. To do this, spool from reel #1 to reel #3 (mono will be backing). Then spool from reel #3 to reel #2 (spectra will be backing), then finally from reel #2 back to reel #1.
This seems kind of cumbersom and lots of winding, but if you want to get the reel full and have the most backing under the spectra this works really well.
David