Spray silicone is not recommended because it ultimately hardens the fabric, providing less 'stretch' and greater chance of material tearing. This is why silicone impregnated fabrics exist - silicone is injected between the threads which still permits some level of stretch / strength, while also providing a level of waterproofness. Otherwise, the spray silicone is crap for most applications. Plus it adds unnecesary weight, and its all about lite gear.