There are probably better ways of making workable bomb bay but this is how I build a simple functioning bomb bay keeping the part count down. Hope below is useful to someone, any questions feel free to ask!

1 - Thin the fuselage height where you want the bomb bay to be and change the rise to keep the surface level. You may need to change to width so it ‘looks right’.

2 - Add thin sections that meet the outline of the non thinned fuselage section using the nudge and rotating the axis. You can do many of these to create a smooth surface or keep it simple and have a slight crinkly outline. I opted to do the ends of the bomb bay first and will later create the door.

3 - Once one end of the bomb bay has been completed (in white) I mirrored it across and back again to get an identical section to place at the other end (in blue). Note the ‘x’ and ‘y’ positioning should be the same. I then do the same again to get the correct shape for the doors. The door sections lengths are then changed to match the void left be either end. These are attached as a section to a hinge and connected to the fuselage where they won’t ‘stick’ to the rest of the build.

4 - The doors are then nudged into place with the same ‘x’ and ‘y’ positioning. (see red section) Add bombs prior to moving the doors into place.

5 - Always check you’ve not lost functionality by mistakenly ‘sticking’ to something.

6 - Mirror the entire build when your happy one side has been completed in its entirety.

7 - Bombs away!