This is EXACTLY the problem that I had. Well with some "elbow grease," obstinance, and a couple of channel locks and pliers, I was able to get the clamp on. One point that I found myself having to do: I had to turn the metal spacer facing the clamp with the open end out. Also: the Graflex clamp has four "holes" where they would generally lock into a Graflex body; the clamps that I got had a metal lip on each "hole" so I ground them down (a dremel will work wonders). However, with that done, the saber looked fantastic IMO!
Here are some pics that I've got:
With my Dark Sentinel v4
With my matching Apprentice shoto:
Just a bit of info: the Archon v3.1 has Obsidian sound, the illuminated AV switch, AS blade (looks great with my pearl-blue dayblade from one of the other guys), and the card is from Etsy.
This saber is my absolute favorite for cosplay (as evidenced by the pics above, along with the Apprentice shoto that complete my ensemble
).
Good luck and I'd love to see pics of your saber when you've completed your Graflex mod