For leadcore and short coppers I would say yes. The issue with mono is the amount you can put on a reel vs. braid for backing. For long coppers 300'+ i would suggest nothing less than 50# braid.
No need to "split" your copper. Best thing to do to get more use out of a long copper (like a 450) is to mark it every 100' or even 50' (w/ spray paint). It will give you a chance to run it as a 200, 300, etc.