The problem with the pre-soak is that you should then reduce the dev time even more to allow for it. Common sense (that most un-common of commodities) suggests that it really depends on how much agitation you use: one inversion every minute is more likely to cause problems with a short dev time compared to an inversion every 30 secs - even less potential problems with continuous, rotary, agitation. You do need to get your timing right for consistent results though when the fill & dump of the tank takes a substantial percentage of the dev time (stop and fix are nowhere near as critical of course).
If it works, it works. Sounds to me like it worked...
Nice one, have fun. Cheers,