The Texas Tornado at Six Flags Astroworld has an inversion that is similar to a corkscrew. It at this time runs with OTSR but originaly only had a lapbar. Here is a decent photo of the inversion : http://www.joyrides.com/sfaw/full/texas_tornado10.htm
An even better picture: http://www.joyrides.com/sfaw/full/texas_tornado3.htm
*** This post was edited by JeremyG on 2/9/00. ***
I think the worry about a corkscrew and OTSRs is that some will get caught in a full lateral position, where the lap-bars only restraining ability is friction.