Not 100% sure on fitting a belly pan with this particular exhaust. It will fit on the 3, but the 4 might be a little wide. Same with the dual outlet oval, clearance on a belly pan might not work out.
One of the things I like is just the sheer volume of air coming out of the pipes. Since its directed at the ground anything like dirt/dust/leaves gets blown away. The bike now has a twin jet wash swirls behind it now
The video clips don't really do the sound justice. It has the same growl but you don't get the bass that you get in person. This literally shakes the pavement and sounds like a cross between a muscle car and a race bike.
I did my own quick sound test just idling in the garage. Its obviously amplified since its in an enclosed area with hard surfaces but stock was around 96-98 db and the RT-4 was around 101-102 db.