How to fix the strapping with stitches and convert the urban backpack into something that can be tied...

From the perspective of lightness and labor saving, I did not buy a photography backpack, but bought a 24L urban backpack. This backpack does not have straps for binding a tripod. I originally wanted to buy two straps myself. It is fixed to the bottom of the backpack, but others have told me that if it is sewn by hand, the bottom will shrink into a ball once a heavy load is loaded, which will be ugly. However, when using a sewing machine, the bag is too deep and the sewing machine needle cannot reach the bottom of the bag and cannot sew. . Could anyone who has modified a backpack give me some practical advice? How can I fix the straps flatly to the bottom of the backpack without getting wrinkled? For example, what materials should be used to make the sandwich or other methods? (Needless to say, it is recommended to fix the tripod in other positions. Only fixing it at the bottom of the backpack is a more reasonable and feasible position: the reasons are as follows: 1. I tried binding the tripod to the side of the backpack, but the force on the shoulders felt uneven. My shoulders are very sore; 2. I also tried fixing it on the front of the backpack. Since the fabric of the backpack is not as stiff and thick as the camera bag, the backpack will be completely dented when a tripod is placed on it. Moreover, the tripod will fall very annoyingly, which will damage the contents of the bag. Threat of SLR.

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