Yes, one could go to an upholstery shop, or sell it and replace it with Boss seats nitrous compartment seat, which is eccentually the seat you have now... that has a larger cavity where your seat trunk is now, and looks exactlly the same.
Another reason for having it under the seat is out of site.... out of mind.... one never knows
I have my 05 900 clutched so that my rpm is 7800. This is the rpm I want to be at full throttle. When I hit my Nos button my rpm goes up to 8200. In my opinion you don't change your clutching for Nos unless you are hitting the rev limiter. You are only on the nos for less than 10 minutes a day so your clutching should be set for no nos.