Fitbit Charge HR Strap Grip Replacement

FIRST VERSION:
The original strap has a retainer that engages the excess end of the strap from the outside of the strap. With this replacement the retainer engages the leftover of the belt with two pivots —instead of one— from the inside of the belt.

The piece is slightly curved and the pivots point diverging from each other, so it is necessary to use support.

The edges that are in contact with the skin have been chamfered but surely not enough value (it seems necessary to soften them a b