Me and my friends are undergrad student in computer science and making a small quadcopter for delivery purpose. We want to make it durable enough to lift 2kg and still be lightweight.
Here's the combination we chose:
Emax MT3515 motor 13g each
12000mAh 4S 15C LiPo battery 800g
12" - 14" Propeller 4.7" pitch
550 - 600 mm diagonal length for frame

The problem is there are no shops / facility selling / providing carbon fiber fabrication. So we chose aluminium over it. We have aluminium c-section channels (1.5cm x 1.2 cm, rectangle shaped) to make the frame. using a universal motor mount on ends of channels will work or not?? We want to make H frame for more structural strength.

Why not get some ready maked frame?

Just quick search shows that there is 550 frames available like this https://ru.aliexpress.com/item/ZD550-ZD-....54.RYHG7O

Aluminium is a good material for things that fly. For the weight, it's very strong.

I'm not sure about C-section profiles though. There may be problems with torsional rigidity. It's probably best to have a look at different profile shapes in the same length as you will need for the arms and evaluate them in terms of weight, longitudinal and torsional rigidity. The last thing you want is for your arms to start twisting when the motors are asked to deliver a rapid increase in speed!

I'm with ELK, a commercially marketed CF frame would be a lot cheaper and more efficient. However, there is the satisfaction of designing your own frame.