We know Stealth has been recreated several times, but it's not such a bad thing for Steve to add it to his collection. Another thing Steve said that most of the other Stealth recreations weren't particularly accurate, although I've never looked at the others.
The next pack to be released (either this weekend, or next week) will be Batwing. Unfortunately, there hasn't been a whole lot of info to go on. The video on the official site doesn't show a whole heck of a lot. There was an artistic rendering of the track, but to the best of my knowledge, Batwing hasn't started construction yet. Unfortunately, RCT has its limits, so Steve can only recreate to a certain degree of "accurateness".
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RCT Station - Home of Steve Franks' Real World Track Packs -
http://rct.gametropics.com