These spare straps do exactly what you want them to. Had them as replacement from the originals on my carbon fiber Gewa case and didn’t even need to adjust size, it was perfect straight away. The hooks are slightly smaller than the originals but the extra security wires makes it all feel very safe. Wearing my instrument on my shoulders now feels like I have a brand new case which is really nice.
The downsize is the cost, I really can’t see how they can justify the price tag, if there was any legit competition I would have ditched Gewa straight away.