Attached is a pic that I pulled from a 1997 issue of Scale RC that featured an article done by Mike Cherry on gear door sequencing as done on his competition Avonds F-15.

Looking at that article and viewing the setup shows how things change rapidly. With todays new door sequencers, it makes Mike's system sort of obsolete. Although with the new style regulated Robart retract valves, it could still be a viable alternative.

According to Mike, it was a very reliable system.