On my 2011/12 RTV 900 the seat was contoured and it would puddle rain so be cautious of that.The rain would get your pants wet in no time even with a roof if it was stormy. The biggest problem I see with the bucket seats is the necessity of tilting over to the steering wheel to get to the radiator opening under the flap . The bottom would really need to be seperate to get decent access. If you have the 08, it may have the plywood base like my 05 did ... it rotted , my 2011/12 had a plastic base and was good but for the water holding contours and the cracking . I recovered it.
In the end, I'd get it recovered if it were me ,with a recommended foam.If you could find a seat bottom that you could tilt, like on a lawnmower, I might consider that. Good Luck, bordercollie