[Fixing items] Changing elastics on Putumayo's Cat Window OP

The most awaited time of the century arrived: the time I was going to have enough courage to deal with Putumayo's Cat Window OP elastics. I know I already bought it with the elastics bad, but along the years I postponed fixing them and it got in a point it was impossible to me to wear it.

In the end, it wasn't hard at all, but even stretching the elastics to the maximum, it didn't fit well the mannequin, but instead, two or three fingers loose. As the mannequin is smaller than me, it fits well my body, but I'm concerned that if I lose weight I will probably have to alter the dress or even sell it...