windshield sealant

I must disagree! Large "frameless" fish tanks are made using only glass and silicone sealant -- these can hold hundreds of gallons of water
Completely different situation. Windshields suffer huge temperature changes, and are subject to vibration and shock.

The answer? "I don't know". I made the mistakes of letting "professionals" install mine and it's starting to look like one or both (windshield, rear glass) are going to have to come back out.