F-G-M-I-O is very 'passable', provided that you have two or less CLT in your fleet. If you really want to bring all three CLTs, then you can only go the middle route to reach the boss node (F-H-K-M-O).
I've used the following fleet composition to go F-G-I-M-O many times:
Main fleet: 2FBB, 2BB, 2CVL
Escort fleet: 1CL, 2CLT, 3DD
P.S. if many people have confirmed that it is possible to go down a certain route, then you might want to take a look at their notes and fleets, and recheck your own composition before writing it off.