I have the FM-B set which are gauged .049 .069 .089 .109 .128 on my SR5 and the FL-B set on my Ovation acoustic 5. There is a considerable difference in the feel of these two sets. The FL-B set is, in my opinion, a much lower tension set. I've never put that set on my SR5. The Ray has the FM-B's (obviously) and the sound is HUGE! So, if you find the FL-B's to be a bit thin, try the FM-B's.
As far as the size of the B, you will notice it, but once you hear it you will be happy it's there! It will rattle your teeth out of your head! I tend to readjust how I play songs so I can work off of the B string. You just get so much bottom to any note you play on that string. In fact, I have a piece I'm working on now with an E octave drone where I actually capo the neck at the 5th fret. The difference between playing the open E string and it's octave on the D and playing the 5th fret E on the B and it's octave on the A is absolutely...

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