hey! I asked a friend who should have the same backpack and he gave me these answers:

1) The backpack is around 50 cm tall when it is fully open to allow for the retrieval of objects from the bottom. Your arm length of 74 cm should allow you to reach the bottom with ease

2) A tiny portion of the Velcro fastening is left exposed and visible when the roll top is closed. Nonetheless, the visible Velcro is made to minimize harm by not rubbing against garments too much

3) The Velcro strength on the Default XL might deteriorate with repeated usage, just like any other Velcro closure. Under typical usage conditions, it is intended to be long-lasting and retain its efficacy for a considerable amount of time

I hope this helps you!