I will let @stevieanswer the driver question but I asked the question about the handle last week. One of my amps has only about 4mm clearance. The answer was, and in hindsight I agree, that rebating the handle will create a dust trap as the handle is rounded over at the edge.
Having used that handle now on my previous cab for 4 years or more, I can say that it is the easiest one hand lift handle I have used.