Which is why i was wondering about interactions with weapons. What happens when you hit a space-timey-wimey thing with a relativistic chunk of matter? With a laser? A plasma bolt? A "death" ray? Does the space-timey-wimey bubble decrease the weapon's effect, or does the weapon make the bubble (and the ship inside) go "poof"?
The way i've been using SFB is to "stutter" across hostile areas: travel towards a destination, and stop and hide when within one spacelane of a hostile fleet. When the hostile fleet moves, the SFB moves on. Hostile planets don't seem to care about SFB, so they can be used to infiltrate/colonize "behind enemy lines" where normal, non-organic-with-stealth-parts ships would be hunted down by the hostile fleets. Live players may defend against this better than the AI currently does. And, it is a nuisance to have to stop and wait, but against AIs, it's usually effective in the long run.
SFBs take about 8 turns to research if you do nothing else. Symbiotic hulls with Electromagnetic Dampening take about 25 turns. If i'm going organic hulls and especially if i'm going to research Active Radar anyway, i usually skip SFB for stealth colonizing.
But, in my experience with organic hull lines, they just can't hold up to SGH or larger robotic or asteroid hulls. I often start with organic, then switch to SGH when it's time to start conquering other empires in earnest. In my experience, the flagship organics need to be either faster to produce, cheaper, or both. Maybe i just haven't learned how to use them properly, but:
Sentient hulls take 225 turns to research, if one researches nothing else. They take 3 shipyard upgrades. They take 8 turns to build. They start with 12 structure. They take 45 turns to reach 57 structure.
SGH take 70 turns to research. They require only 2 shipyard upgrades. They take 2 turns to build. They are 100 structure immediately.
In the time required to build a sentient hull, one can crank out 4 SGH. While it's true that quality can overcome quantity, quantity has a quality of its own.
If switching hull lines was hard, and i was a supply-restricted or sneaky species, i'd probably start with SFB, then do full robotic, and never look at organic.
Any non-sneaky or non-supply-restricted species, i can't see why i'd consider organic at all.
Again, maybe i'm just bad at using the organic line to it's best effect.
PS: to determine number of turns, i just started a new game, the clicked "add to top of queue" for the particular hull, or hull + ED.