I just boosted crew for the first time (my IJN engineers). They are lvl 72.

Obviously, their ability grew by 20%, which is about 300 displayed ability (from ~1500 to ~1800). Similarly, their growth went from +25 to +29 (that's and extra +4).

Now, had I hypothetically boosted them at say, lvl 1, their growth would have gone up by 20% of +11, so by +2, and the 20% extra ability would have been fairly meaningless. given than they would have (hypothetically) had +2 per lvl, they would by now have 72*2 = 144 more displayed ability... HALF what they got from being boosted at lvl 72!

So to me it seems that the later you boost a crewman, the more benefit you get, because 20% of the accumulated ability will always be more than an earlier but much smaller growth boost, no?

Or am I missing something?

What's the best timing to boost to get the most benefit from it?