I've actually stacked all three before: tirz, sema, and reta.
You could keep your tirz at 9mg/week (4.5mg x 2) and just add sema in the middle of the week.
Have you used sema before? It can be pretty strong (more so than tirz and reta imo), so if you haven't, start with a low dose like 0.1mg a week, then increase to 0.3mg, then maybe 0.6-0.8mg. See how you react.
A once-weekly dose of sema should hopefully curb your appetite.
For me, sema is the best for suppressing hunger, but you really need to increase the dose to feel it. At 0.1mg or 0.3mg, you probably won't notice much difference in hunger or food noise (you're basically just getting your body used to the drug).
If you've tried sema before, you could start at 0.8mg once a week.
Medical research shows that therapeutic doses of sema start around 1mg and up.
When I started ozempic, my doctor started me at 0.1mg, then 0.3mg, then 0.5mg, then 0.8mg. I really started seeing benefits after 0.8mg a week.
I noticed the most food noise reduction around 1.3mg a week. Eating a small meal filled me up for the whole day, and I couldn't eat anything else! Food actually grossed me out, it was amazing to experience what normal people feel like when they eat a small amount and feel satisfied.
But at 1.3mg, I started feeling really sick with constant vomiting, so I had to back off. For comparison, I can handle 10mg of tirz and 7mg of reta without any issues (but those aren't my current doses).