Thanks, John @Johnb. So many times I've wanted that effect because one time I created it accidentally but never could figure out how I did. EZ now.

John vd Biggelaar (@johnb)
If you don't have access to the plastic tubing, you can try to center the kit supplied exhaust parts in the opening. I try to place them a little bit closer to the front edge of the opening, closer to the engine.

It is indeed a very kind gesture for our friend
Spiros Pendedekas (@fiveten)
to send you some tubing.

Here is how I do it when I use the kit supplied parts. You can paint the rest of the opening a darker gray / off black color to make it look like a hole, which on the real plane it actually was.

This replicates the room needed to clear the exhaust pipes as the engine shakes / vibrates when it is started up and running. If this extra space was not there, the exhaust pipes would hit against the aircraft skin.

Spiros Pendedekas (@fiveten)
Your exhaust system looks incredible ! Very lifelike... and much better than anything I have done on any of my Corsair builds.

This morning I remembered to still have a box containing various sizes of heat shrink tubing. This material is flexible and easy to cut so I gave it a try.

At first I thought the material might be affected by the glue but that seemed to not be the case.

After painting the background surface blackgrey as proposed by Louis @lgardner.

This is how the exhaust pipes look like currently. There is still sufficient clearance as was with the real aircraft. Although I still have to paint them with a burned metal color, I think they do look better than the original undersized exhausts.

1 additional image. Click to enlarge.

The upgraded exhausts look superb, my friend @johnb!

Painted the struts off-white and the brake line black.
Just a bit of weathering to be done.

John vd Biggelaar (@johnb)
Wow ! The exhaust is a huge improvement, and the brake lines look equally as amazing... 🙂
Keep it going my friend !

I'm glad the pictures helped.

All those details are looking great, John! I like your new exhausts.