NO. The spools for the Stradic FG do not fit the FH for sure (I tried and stack up is way off). I don't own the FI, but am sure they will not work with the FH. Evidence is how the drag assembly is all different (new FI are waterproof and the older FH were not and so forth)
Shimano when they change the model line it is as if they bump out the oldest and lowest on the totem pole and shift the next one down from the top of the line. The consumer gets a much better reel, but you also have to pay a bit as well.
I have some old Stradic 8000 FG spools and they do fit/work on the Shimano Spheros 8000 FA (may need a thin washer or two below), but the drag isn't waterproof. I have mono on them and use them in case of emergency.
Seems like shame to toss out the old spools.
Too bad no one ever took time to do some kind of cross reference chart w/ spools. Put the spools up for trade w/ some one who may be looking for older spools.
Threaded Mode