How would you do it?

If you're looking for an inexpensive solution, pick up a set of mixed sizes, black elastic hair bands at your local box drug store.

(See pic of USN speedboat OFC I repainted.)

You can also buy scale chain - I believe Model Tech Studios has some.

Good idea, will try and steal a couple black ones from my grand daughter, the pink glitter ones will just not work.

The hair bands could work for the boat because they use heavy duty straps.  You might try a flat sneaker lace.

I like the chain for the helicopters.  I did this for some Caterpillar vehicles.

Go to the jewelry aisle in Michaels.  All sorts of inexpensive chain necklace that is great to model O gauge tie down chains.

@Ron045,

Do you know the size of the links?  The big online store has big rolls, cheap, in multiple colors with 4 different sizes ranging from 1.5 to 3.5 mm.

@texgeekboy posted:

@Ron045,

Do you know the size of the links?

They have many different sizes.  Here is what I used.

@Ron045 posted:

They have many different sizes.  Here is what I used.

That is perfect for the helicopters.  I'm going to get some of that. I would not use them for the boats. Find some kind of straps.

I got the 6819 helicopter car as a NOS purchase at an auction (yeah, I spent too much) a few months back.  I never liked the band to hold it in place, so I just bought some jewelry chain and will upgrade it after it arrives.  I have a bunch of other cars with loads (military vehicles, rockets, etc.) that I plan on using it for as well.  Thanks for the OP @CALNNC and pointing me in the right direction @Ron045.

I used a chain as suggest by @Ron045, along with some modelling ship rope, to secure the helicopter and propellers.  The before/after pictures are below.  I saw several model train pictures where the chains were pulled taught on the struts, but I could not do that.  While it's not as good as some have done, I think it's better than a rubber band!

One interesting note, I did numerous google searches for helicopters being transported via rails, and could not find one picture.  There were a few (very few) of them being transported by trucks.  Most of those showed them with the props removed.