Let me tell you the story...
I work at Level 3 server technician, and I am quite fastidious with trying to ensure we have no problems in my company. We have Mimecast, Meraki (advance license with AV & Malware protection) and Trend AV. A company informed me that I was passing Malware. I checked my laptop with Trend, and tried your free program...nothing! Strange, until I thought about my USB Key, with 200 Malware on it, which I only use for clients. It had somehow passed to my key, and why I was asking whether your program supported USB on insertion. If it had, then you would now have another customer. I can scan the USB at any time with Trend AV, BUT, USB on insertion would be a good selling point for you!