Are your current racks sealed? The main problem I see is that hatchlings are usually kept in 6qt tubs which are ~12-13" long and at the back end your making it 91-92* so with a sealed front there isn't enough heat transfer, especially if the room is 80*.
I think the best thing is if you can complete this a month or two before you need it. Then you can measure temps and add holes to the front slowly until you reach the desired temps. Just because of the small amount of airspace in hatchling tubs and the needed hot spot, this build seems like it would be better in a room without so much outside heating.