Mandy makes an important point. The dose-response data I cited are population means. Individual variability in GLP-1 receptor sensitivity, gastric emptying rates, and metabolic adaptation means that some people genuinely need 2.4mg to get adequate effect while others plateau at 1.0mg.
Kev, if you're still losing at 1.7mg, there's no reason to increase right now. If you hit a true plateau (4–6 weeks of no loss despite adherence to diet), then 2.4mg is there as an option. It's not now-or-never.