Let's not be hasty. If AT is to be trusted, then prototyping the cueball would give you a perfect, reliable source of knowledge about what's going on. But then, all of the game's enemies would become omniscient! You should at least wait until after entering to go through with this.

Although... Isn't at least one of the prototypings guaranteed to be something dead?

So, if you were to throw in something random pre-entry, you may face some sort of predestined circumstantial sabotage on your ability to choose your second prototyping. Maybe a time traveller will appear to make sure things go their way. Maybe an unlucky bird will experience a sudden heart attack mid-flight, dropping straight into the kernel. Maybe you'll accidentally step on an ant, slip, and fall down, unintentionally launching the squashed bug spriteward. Regardless, it seems the best move might be to take initiative and throw in something dead now, to save your non-dead prototyping for post-entry.

But the only dead thing around is... well...