www.pirateship.com/rates site is well known by now, but even with that discount, you'll spent $10-$12 shipping a glow engine out of state, plus a premium outside the CONUS. Priority Mail packages and envelopes are free. The lowest rate that offers room for a glow engine is using the Flat Rate Padded Envelopes that ship anywhere in the USA for $8.30, and a little extra for insurance but $100 value is included.
Here are photos of how I practice this using an OS 61 engine and muffler. Using old incoming Amazon boxes helps keep shipping costs down.

What enters people's mind when they ship like this?
Do they understand that perhaps people buying 55 year old engines, might just want to display it,
and would like to receive it just as it's shown in the photos?

Plastering packing tape all over a box, is not cool.
Don't do it. It's inconsiderate.
This makes THREE TIMES now in a month.
I talked to a seller about it,
"I sold over 100 engines boxed this way, you're the first to complain."
All my fault then. Too picky I guess. Rest assured, I'll never do this to anyone.

Worst one, Senior Falcon, $300,
USPS postage taped right on the factory box.
And I thought brown paper was a stupid move? No reason to out anyone, everyone else deserves a turn,
and I'll be that one guy who complained.

I receive items improperly packaged, I'm sure you have seen it happen at least once. You don't want to use Wal-Mart bags. Damage claims would be denied. Avoid large voids in the box so things inside don't move around unprotected from damage. Packing a box firmly, so nothing is shifting around or preventing the lid from pushing down when you press on it a little, is what you want.
Bubble wrap, foam peanuts, shredded paper, are all suitable. I use bubble wrap. Transmitters are one of the more fragile items to ship, levers, switches, and gimbal sticks are easily damaged in transit. The handle mounted to the plastic case can break too.
$1.25 at the Dollar Store, buys those foam float sticks for pools and ship at least 10 small packages before you run out. I cut 2" pieces for the gimbals, and 4" piece for the antenna, and wrap it all with bubble wrap to protect it.
Office Depot sales are nice. Walmart runs sales too.
Cut down your box to the size that fits the radio and the shipping fee will be less with a smaller box, Priority Cubic or UPS is the best shipping method.
www. Pirateship.com or ShipStation works too, any online shipping label is less than walking into the post office or worse, a Pack and Ship place.
Your ratings will reflect the difference compared to what your buyers typically see. Hope this info helps.