New member here, bought a used ('08) K12GT last month, put a thousand miles on it so far. Just back from a Bill Mayers Saddle ride-in visit, thought I'd make my first post...
After a few days riding, I knew this bike needed a better seat to turn it into the asphalt-eater it is. I got lucky and ran into a K12GT owner at Alice's who let me try out his seat, and I then decided to give BMS a try. It was a 750 mile roundtrip from the SF Bay area to the Ojai shop. I left Tuesday, got a hotel room, and arrived at BMS at the pre-arranged 7am Wednesday morning arrival time. The shop had three ride-in customers for the morning session, I was the first to arrive, and was done and out the door by 11:30am. The guys in the shop work on several fittings at a time, and really know their stuff. Don't second guess them, answer what they're asking, and be specific. I had 4-5 fittings and two test rides before we agreed we had the design right. I just had the front seat done in a matching vinyl, and am highly pleased with the outcome. I knocked off the last 4 hours/ 250 miles non-stop on the way home with no issues. I'm an aggresive twisties rider, as well as a long distance tourer, and needed a seat that worked well for both. $450 well spent.
Here's my stats: 6'0", 31" inseam, 175#. I'm a forward, upright sitter. With a long torso, I have to reach for the bars even in the full back/up position, so I ride pretty close to the tank. For my height, the upper seat position worked better, but the lower/forward seat position put me in a preferred location. My problem was when sitting in the upper seat position and sitting on the front of the seat, the front of the seat pan dug into my legs, on top of the usual hot-spots created by the OE seat. So the solution was to built up the seat foam to the high height but but with the pan in the low/forward position, while adding some tractor-seat shaping for support. BMS has several different density foams, we went with the medium/firm for the "saddle", which is then covered by two other layers of thin "magic" foam (my words, not their's). The customer is actively involved from start to finish, and everyone is pleasant to deal with.
Rocky (Bill III) Mayer is familiar with the K12GT, as he has one in his current stable of bikes. It's currently for sale, and he says he'll throw in a custom re-fitting of the BMS seat on it for free ;-)
Two unexpected benefits - the ride harshness in the 'Sport' mode is gone, and the seat heat feels more evenly spread out instead of just burning your two seat-bone contact points.