Good luck with your new jet, it may fly better than the Skymaster. I would replace all the air line anyway, see some Robart stuff in there and who knows what else.
Engine compartment hatch
I like to use a separate air valve and supply for the gear, doors and brakes. If you lose an air cylinder and all the air is gone from the doors the gear will just push the doors open.
Pull everything out and make some nice trays, it will clean up nice.
My new Skymaster F-18F is on the way here, ordered the one in stock at Chief, it's my opinion after owning both, that the F is a much better flyer. I hope it works out for you and you have a lot of fun with it though.