Used tons of different insulin syringe gauges and lengths. Honestly no noticeable difference between them. Never dealt with bruising problems either. I went with 30g by 1/2 inch for peptide injections and haven't looked back.
Haven't flown since starting Oz, but I'm down from around 370 to 255 and the extra room in the seat is real. At 6 foot 4 I still can't stretch out completely, but honestly I'll take any win.
4 weeks is pretty short. Plus you ramped up pretty fast, so your body's probably lagging. Some people don't feel it till they hit 1mg or higher and stay there for a bit. True non-responders exist but that's usually less than 5% weight loss after 3 months on a real dose. Give it more time before...