Estes Super Orbital Transport Build, Kit #7314, Part 3, Engine Mount & Balsa Prep

The lowest engine mount centering ring will be even with the end of the body tube and visible on the finished model.

TIP: I'd recommend sanding the face of the lowest position centering ring flat. Smooth out the wrap ridges and removing any remaining green off the face. You can also do a smooth coat of wood glue and sand that flat. Your finished model will look cleaner.

Note the cut angle of the engine hook notch in the lowest ring. This makes a square notch when the mount is glued up.

TIP: A piece of tape will keep the open notch closed as the glue sets up.

As mentioned many times before - 

Laser cuts are wedge shaped. Sand the root edges flat for a larger, flatter gluing surface against the body tube.

I didn't remove the laser cut slots from the main wing. After many notched "tab and slot" builds, like the QCC Explorer and Low Boom SST, I found the low tabs and notches take a lot of extra work to fill after assembly. 

Especially if the tabs ended up below the surface of the adjoining part face. It's up to you-

I sanded off most of the slot tabs on the engine housing Parts AA, N, O and Z. 

Tab/slot construction is easier to line up the parts. I had to draw up a positioning template. 

Some models require tabs for strength. On this build I figured the engine housings would be strong enough doing surface gluing.

I did leave the tabs on Parts R (wing tip) and Parts H (Wing) where I felt a stronger notched outside joint was needed.

On the outside (Part R) wing tips and the outside notch of the wing (part H), 

Leave the long edge of the tabs as they are - long with no removal of the burnt laser edge.

You'll have less of a seam joint to fill if a (longer) tab is sanded to surface after gluing together.

Built a I did, the engine housings glued under the wing will be a surface mount (no tabs) like the original 1969 kit.