Any way you go about it, you're going to have to do some figuring and a little alteration to either the badge or the kilt. Here's my throw-in:
If the badge is never again going to be worn as part of a uniform, and if the only use it will see is as a kilt pin, and you're probably the only one who will use it, then I think I'd go ahead and cut the post off of it and solder on a big safety pin. That might cut down on some of the weight, you'd have an item that you can use, and you won't have damaged the front side of the badge.
And take pictures! :D

I agree. You have to alter either the kilt or the badge. I would put a bar pin on the back of the badge. Even if you put it on a hat or whatever a bar pin would be a viable way to attach it to virtually any fabric.

http://www.jewelryfindings-online.co..._pin_backs.htm

Personally, I would recommend contacting Alexis Malcolm of www.AlexisMalcolmKilts.com, and seeing if she can do something to help you, if you haven't already altered the screw post of the badge. If you visit her website, you can see that she has mounted Marine Corps collar emblems (and devices from the other four armed services as well) to standard claymore-style kilt pins which will not cause you to dig a hole in your apron. The standard eagle, globe and anchor collar emblems have the same screw post that you describe, and she may be able to alter one of her kilt pins so that you don't have to solder on the badge or destroy the screw post to achieve your desired result.

OR, EVEN BETTER, if you'd rather have that affixed to a belt buckle, she can absolutely do that with no damage to the heirloom whatsoever. She'll just drill a hole in the belt buckle and you can affix the round nut to the screw post once put through the buckle plate hole. Depending on the size of the badge, that might be your best option.

I'm just a newbie, but I looked long and hard for my current kilt accessories, and her stuff is pretty good. She might be able to help you out.

Again, there is no need to alter either one. As long as you have a thick, sturdy backing, the same size as the badge, there will be no damage to the fabric, provided the fibers are only moved to create a hole. The weight of the badge will be supported by the entire piece of fabric that it covers, not at the post. In fact, if you catch it on something, it will be far safer than using a pin back because of this.

I move mine between my kilts routinely, and it is impossible to tell that it was ever on a kilt when I take it out. I have to repart the fibers when I put it on a kilt, as well as remeasure where I want it because there is no evidence of the last place it was. All it takes is a bit of care when putting it in, be it acrylic, wool or PV.

Greg I would be very careful about using a magnet. All it would take is brushing up against something and your badge is gone not to be recovered. A terrible waste.
What about taking the screw on washer and soldering a pin on it and then you just spin it on the badge and pin it to your kilt. Seems to me it would work.
See you in Ventura?
Bob