[truckster]

You can use silicone, but there's a reason it's not used for auto glass. It doesn't hold up well over time in that application. You can buy automotive urethane at most parts stores. You could use something like JB KwikWeld. It's a little less flexible than actual channel adhesive, but it should work. You don't need to fill the entire channel; just a couple of inches at each end will hold the glass securely.