To OP:
If you're gonna pick up 4U then you'd be doing exactly the same subjects that I did this year. Having just finished like last week I think I can offer some perspective.
You're in a better position than I was in terms of decision making. At the end of yr 11 I was ranking 1st in all my subjects but knew 12 units would be pretty heavy. Still though, I kept with it coz c'mon... who would drop a subject they're coming first in? But in your case it looks like chem or eco would take the axe unless you know for sure you can pull a 1st (to anyone reading: yes this level of certainty exists at schools ranked ~300... I went to one.)
I would not want to be where I was two weeks ago. I had 4U and Eco in week 2 of examinations (eco is content heavy and kind of a bitch to study for) and then chem, 3U and physics in the 3rd week. I was stressed beyond belief and I think the extra 2 units diverted precious study-time away from my other subjects. I still think I did well (only time will tell) but I HEAVILY doubt I'll hit my (somewhat lofty) goal which was 95 in all subjects. Would I have achieved it if I did 10 units? Who knows. But I know I would've at least been at lot less stressed
And in terms of subjects: Eco is bae. I loved eco, and I'm a maths and science type person. The exams are usually easy and you walk out feeling quite good and you can get high marks with moderate effort. I poured my heart and soul into Chem and Phys and sometimes the marking criteria just came along and smashed all my hopes and dreams.
ON THE OTHER HAND! I had previously never believed in the whole 'safety net' idea. Now I can actually understand it. You can be thrown off, no matter how much study you do. There were a couple sillies in made in Chem and 3 marks in Physics I legit just did not know how to do (+ other sillies), and I don't think additional study time would've really remedied that. So so glad I didn't drop Eco (which is what I would've dropped if I had gone for 10) cos I think that's gonna make up for losses in the Science.
So yeah I've probably left you in a worse situation than you came in LOL. Sorry for the rambling but it's honestly a question I struggled with all year.
TL;DR: Stress vs Safety. You decide
And oh the days when we aimed for state ranks. How innocent those days were.
