I tried experimenting with a few different strats for marble 3 but it turns out it was a lot slower, the only bit I borrowed of JXQ's run was the 3 hit on rototnik. I'm now at the beggining of Spring Yard 3, which shouldn't be too hard as I'll go for the 30 secs, I seriously doubt it can be completed in <24 secs + 50 rings.
http://rapidshare.de/files/22987002/Sonic_the_Hedgehog.gmv.html
Just two stages left before I start again, although marble 2 needs a proper look into for the ring route + the last three special stages.
Edit: OK I done Spring Yard 1 which didn't pose too many problems, I got a frame perfect 30 seconds this time unlike Green Hill 1, I'm not sure if its possible to get <24 secs.
http://rapidshare.de/files/22998813/Sonic_the_Hedgehog.gmv.html
I haven't had a proper look at the 5th special yet but it does look complicated.
EDIT_2:
OK I did the 5th special and I personally thought the previous one was harder but here it is. The collision system for that level is dodgy and unfavourable.
http://rapidshare.de/files/23019870/Sonic_the_Hedgehog.gmv.html
Just one last stage.