If your 45# bow/arrow is in tune now with 175 gr points, I'm sure an otherwise identical bow at 50# will be in tune with the same arrows at 125gr (+ or -). Whether that's the direction you want to go is a different question. Usually, people go up in weight to hunt, not shoot targets. Usually, people want heavier broadheads for hunting. To keep your 175 gr point weight, you might have to go up in spine in arrows.
If you're pulling your 45# bow easily, maybe you'll pull your 50# bow to full draw. Sometimes if people are struggling getting the bow back, they might not quite make it to full draw, in which case the increase in poundage is somewhat less than marked.