I live in the general Seattle area. The shop you mention (Rich's), does custom work. Generally you take your bike to them and they fit you to your seat. They will remove material or add material to fit your bottom and riding position. They will add gel-pads and custom piping (trim); their preferred fabric is usually leather. I would hesitate doing any alterations to the seat other than maybe changing fabric or color. You may be safe just adding a gel-pad but any other alterations to the foam padding would not be a good idea unless you are there with your bike. They’re real specialty and where they really excel is on cruisers and touring bikes where there is a lot of material to work with and they can truly customize a seat for you. I had them alter my seat on my BMW K1200 G/T. They removed material to lower my footing and create a classic cup shape, than added a gel-pad front and back. They covered it in leather with blue piping for the finishing touches; it looked great. I now have an $800.00 seat sitting above my work bench on a shelf that has less than 2 hrs. sitting time! Too much material was removed and when I took it back I was charged additionally. I ended up ordering a seat from Sergeant’s and it was perfect for less than half the price. I learned a costly lesson!
I’ve also bought seats from Corbin and I’m not exactly convinced they are the best option for sport bikes either. They use a metal pan that is usually heavier then your stock seat. On my Suzuki SV S650 the holes for the brackets didn’t line-up exactly right and took some additional modifying on my part to make it fit right. I did get a very nice Gunfighter seat from them for my VTX 1800 before I discovered sport bikes.
My recommendation if they could be talked into helping us would be Sergeant’s; their specialty is sport bikes first and everything else second. Their seat-pans are light weight plastic and they highly recommend vinyl for wear resistance as well as durability against rain and getting wet.
In my opinion if anyone could make a comfortable seat without it looking bulky and for a reasonable price it would be Sergeant’s.
No first-hand experience, but the majority of the reviews of their work I've hear are positive. From what I've been told, you really have to be there in person since it's a custom shop, as 2wheelcrazy said, it's not really a mass-production setup. Without any off the shelf options for us Brutale owners, I may give Rich's a shot as I don't think the stock seat is going to cut it for me. But I have a few other things I plan to to do my Brute before I deal with the seat...
For those of us in the Seattle area Rich's is a good option since we can be there while they are working on the seat and can provide guidance as to what we are looking for and that's something they want you to do so that it is truly custom to you. As I already said I would consider having a large gel-pad installed and reupholstered but I already know from experience it’s an expensive bun holder when they had you the bill.