Well done, it's best to have the sponge just a bit bigger. Alternatively if you cut a piece of wood or ply that is a loose fit, then you can wrap a piece of cardboard around the wood to squeeze it in. It IS a bit tricky measuring it & seeing how it fits without a veil. Next time give the bees some smoke, it will drive them in & give you a better chance of fitting the sponge or ply before they come streaming out.
I have some one inch foam soundproofing leftover from soundproofing my boat motor. I cut strips off that. That's running low, so I cut up ply strips & fit them to customers hives before they pick them up. I leave some cardboard sticking out so that all the customer needs to do after the hive is in position is pull on the cardboard & the piece of ply comes out with it. I have it tight enough so that it can't come out during transport.