I know the STM fits on the 8 & 1000 laydown motors with twins, but not sure about the older 8 if that's what you've got.
The negatives of the valve delete are greater as the motor gets smaller, as the bottom end loss is more obvious. I know people with 1200's with the deletes that like them, but fewer 1000's that do, and I don't know anyone with the 800 that likes them.
I've owned two sets, and don't have a "problem" with them, but would not recommend them unless you're a very serious weight watcher & are willing to compromise runnability for weight.
2011 CF8 LE 141 Cutler stage II race gas turbo, powerclaw track, BD-X oil delete, Koso egt, Bparks light weight bushings, BD-X inner wheel kit, BD-X 2 wheel, BD-X anti-stab, BD-X 40" A arms with 19" floats
Wildchild T top post with 4-6" Rox adj riser, protaper bars, cycra handguards, pro design tether.
BR-tech Thrasher hood and venting.
And a throttle that points the RIGHT way, FORWARD!!!!
250++hp...and still quieter than a sled with a can!
2012 proclimb M800 snopro, BDX oil delete, CE 2.5 track, 38" arms, wildchild post mod, pro design tether, and a hot dogger (and of course, a forward throttle...)
PM me if you're looking for lightweight or diamond drive parts, I can get you discount pricing on BDX parts.