I would do something like this to the pad. I've seen many people run without the pad with no problems, but it keeps the heat from your outer hood, and it's also a fire retardant in case you ever should be so unfortunate.
Without the Vent system it's doable with minor modifications.
With the vent system you would have to remove a lot more to allow the system the ability to attach to the hood. It didn't look like it would be worth it when I installed my hood w/vent so I left it off.