Whatever you settle on doing, you should have a limit as to the daily rate of feed. I would start appropriate for the anticipated maximum number of fry. It will ramp up as they grow geometrically. At some point, to grow at maximum rates, you will have to exceed safe limits without aeration and water exchange capabilities. When this occurs you should fix the amount and not exceed that going forward. Monitor 20 or 30 samples each week to determine average lengths and compare their growth against their growth potential. When it falls below the growth curve significantly, then it would be OK to take them out then. Rinse and repeat if season and time allows.

FishingRod suggested incremental harvest. This can work to keep them growing at that limited amount of feed. It's a practice that is put to work worldwide and could help you to grow some into the 3 and 4" lengths. Growth rates will in part be dependent on the numbers of fingerlings in grow out and this can be very variable. Monitoring growth against expected growth will let you know when food is limiting growth.

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers