This machine has app. 8kg.
I went to my fabric shop and I said to the shop owner, "I need the strongest Velcro you have". And then I got this 5cm wide stripes.
This is also one of the reasons, why we have decided to make this wooden basic plate: the wood has no intention to slip on the denim, neither does the machine on the basic plate.
So the Velcro's job is only to close the bag's sides quickly and protect the machine against dust and dirt. It does not need to endure any force.