The best advice I have for soft bags is to purchase a bag that is somewhat oversize, one that has at least an inch or two of clearance in all directions. Then line all the bag's inner surfaces with Ethafoam, which is a closed cell, pollyethelyne foam that is stiff, yet still provides a great deal of cushioning. Place an additional inch of soft foam padding on the top layer to protect the buttons, keys and display. The cost of the foam and soft padding averages about $50 and it will last for decades. My current bag is nearly 15 years old, it is padded as described above, and I think I'll probably get another 15 years out of it.
Gary
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Travlin' Easy
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)