What they said above (they got here first, while I was typing this).
I may not be the best to comment on D, as I am pretty well maxed out at the 300-350' golf-d, unless I unleash a blizzard in a tail wind and really hit it well then I can get 400'+). But I'll make an attempt and wait for the massacre to begin.
When you move to a higher speed disc, you need more spin AND more arm speed. Throwing a more over-stable disc at the same speed as the under-stable disc (in the same conditions) will almost always result in more left finish with the over-stable disc. You also will see a big difference when throwing into the wind vs tail wind (that is for another post), but it definitely changes the "apparent" speed of the disc.
Maybe you should look at something a between the sidewinder and the boss (as these are pretty big ranges of stability and speed).
Once I started turning my sidewinders over, I though I had to go to something more stable to get more d, but I was wrong. I played with a group on night at league and they suggested I release with a little hyzer/more hyzer. This allowed me to "turnover" the sidewinder and still get a nice looking S-line out of it. I added 30-50' THAT night. I eventually moved to more stable discs (than the sidewinder - Startfire/Firebird/Wraith), but when the blizzard plastic came I tried it and am hooked. I don't need to throw as hard with it to get get D and sweet looking lines. That said, you need to really work on release point and snap vs speed for these discs AND they are super effected by the wind at the weight I throw (130's, wanted something that floats).
Ok, that's my $.02, hope it was somewhat helpful.