This should not be a problem with smaller iPhones or other devices. I tested it with an iPhone 4 and it worked great. By tightening the band, the free space on the sides of the case becomes smaller, which means that the iPhone can be fixed well to the arm. In this way, you also gain a little total length of the whole band, should this be tight.

No, my iPhone X with 5.8" only went in when I first "enlarged" the opening a little.

Hello.. Unofficial size of the pouch is 140mm x 80mm (L/W). The phone is 150.9mm x 72.6mm x 7.7mm (L/W/H). Your Galaxy S7 Edge will therefore not fit perfectly. Regards