Place pilots in the gun slots.

As for armor... IJN armor is crap and you can't put enough of it to protect you from anything beyond the basic FF guns.

I'd suggest getting 0.2 or 0.5 belt armor and max possible bulge.
it won't save you from BBs but will help with torps.

looks pretty ok without guns, gunplacement is pretty bad on the hiryu anyways.

you could consider using hh, they weigh little and are of best effect against the only enemy worth shooting at.
might wanna bring a dd with some guns for escort & subspotting (dd1 works ok for it)

but lvling the pilots on your gun slots would indeed be the best choice, since you need more of them later on and you dont want to get in range of a sub in the small cv's anyways.

Thanks for the replies. I think I'll scrap the deck and add it to belt and bulge. My current bulge can survive a few torpedoes so that's helped a bit.