the quick answer is, it depends.  i have installed seats like this and the fact that the bottom of the seat is not shaped to fill in the slight V of the hull is typically not a problem.

that said, i usually don't consider velcro (and an adhesive backed velcro at that)  a reliable way to keep a seat in a boat for anything more than a season....and a light one at that.

what i usually do when fitting out is get the seat adjusted first (location) and then i make my hip pads  (foam pads that keep you centered and that are glued to each wooden hip pads) come down low enough to lock the seat pad in place against the hull.   this way, to remove the seat, you have to basically slide it forward against the friction of the bottom of the hull and the hip pads along its side until it is clear of the hip pads, and then the seat just comes out.

i consider it sort of a safety issue that key pieces of the boat should stay with the boat in a capsize of other rough handling.   velcro used in this manner doesn't meet my standard for that.   you want that seat locked in tight but easy to remove for cleaning and ensuring all water is out of the boat.  velcro attached in the matter described attracts sand and dirt and breaks down relatively quickly when attached and re-attached (which is good practice to clean out/ensure the boat is dry after every use).

h

I have not tried the Creature Comfort Seat but I have tried every other one that CLC sells, and many from other retailers.  For my posterier, the seat made by Redfish Kayaks is the most comfortable.  He custom makes them to fit your kayak and it is likely that he already has the measurements for the Shearwater Sport.  They are not cheap.

Regarding velcro, I am of the oppisit opinion of Hspira.  I prefer to use velcro because it allows me to change seats based upon the conditions and also change the seat position based upon how my kayak will be loaded.  As he points out, the velcro will degrade over time so I replace with new whenever it starts to get weak.  

just a note to echo something mark said above, about redfish kayak seats.  i use them as well and i think they feel great and look great.

you can actually buy one relatively inexpensively if you are prepared to carve the seat to fit the bottom of your boat.  the seat they will sell you will have the top done (its called a pre-sculpted seat blank) and only runs $55.   so you just have to do the work to fit it to the boat bottom which is not that hard if you have a bit of patience and the time.  http://www.redfishkayak.com/foam.htm

i use them with a normal back-band seat and find it works really well and looks great.

mark, i was also a curious about what looks like a bungee in front of the seat on your picture.  what do you do with that?

h

Thanks for the advice guys. That pre-sculpted seat blank looks great and cutting to the floor shape shouldn't be a problem. I'll check with him on shipping to Canada, I don't see any info listed on his web site. 

The bungie is a secure attachment for my dry box.  When racing, I use it to hold a hydration bladder.