Yea i do have that other seat. And i promptly cut it up to make it fit right. I did away with the stock hinges and latch. It never sat flat and wuldnt latch tightly, it was also way too wide at the front to be comfortable. I trimmed it close to the frame up by the tank and then flared it out where my ass started and my legs ended. I wouldnt suggest it based on being a bolt on. I had to do as much work as a "universal seat". It does have a great shape though, i like the longer tail on it, it covers the tire instead of ending at 12 oclock.
I welded a crosspiece into the frame and ran bolts down through the seat to snug it down. I also added the stock "snubbers". The rear needs some more bracing, i'm going to try to brace with one more cross piece near the back of the seat and then some sort of bracing to the taillight housing, since i dont want to have any bolt showing on the side of the seat.
I'm working on a seat right now...so far my materials include...a $10 gel seat pad from Canadian tire. $12 for 4 sheets of 2'x2' garage anti fatigue mats from Walmart, also a $14 memory foam lumbar support from walmart, $20 worth of marine grade vinyl from Fabricland, and a free seat cushion from an airplane or boat or something that i found at work...it says something about being a certified flotation device.
So far there are two layers of the garage mat right on the fibreglass seat. The memory foam sucks, the Honeycomb gel seat is pretty good, but i may throw all that shit in the garbage cause this seat cushion that i found at work loks perfect, and it can be all on its own and shaped, no layers of crap.
I'll take a few pics before i cover it. I got quoted $500 in town for foam work and vinyl for this seat !!