I have both a Pflueger President and Supreme XT (older model from 2013) that came with a spare spool.  Will that spool (Supreme XT) fit my President if I wanted to simply change it out since they are both the 30 size reels?  The spare spool has Nanofil on it and the President has mono on it.  Just wondering if they were interchangeable since they are both Pflueger reels and both the 30 size.  Thanks for any/all help and best wishes on the water!

If the oscillations (how far the spool moves back and forth) is the same between reels

AND

The portion where the line is spooled is the same width between reels. (Gap)

AND

The gap mentioned above is the same distance from the tip.

AND

The drag set up is the same thickness and location within the spool.

(Catching breath)

For example; I have a Shimano Sahara FD that can use (has used) spools from the same era Saros and Stratic.  It can also use the spool from the Orange Sonora model, but I need to use the knob from the Sonora because the drag is different.

Do you have them at home?  You could try the swap and find out.