Hello, the shades won’t fold properly if the dowel comes in two parts. So you can maybe use these dowels: https://amzn.to/3Kn8uxC
Also, keep in mind that if the shade is too heavy it will be hard to open and close, the weight will depend on the size and the kind of fabric you use.
Sometimes is better to make 2 shades for a window instead of a large one.
I hope these tips will help you choose the best option to make your blinds. Have fun sewing.