I'm surprised more people don't utilize the empty space in the wheel well of their spare tyres. I know a standard 1lb U.S. gas bottle would fit in there. And bonus if it's bolted to the front of the bus. No need to cut a vent. Plus, if you have a good head-on collision, well, let's just say you won't wind up in a wheel chair anyway. I love having my tank welded to the underside of the bus, personally. Completely out of the way, plus 3 pounds lasts absolutely forever. And it really is fun having it filled. They always ask me to get my tank out of the van. It takes some doing to convince them it already is out.