Ahh, James,

Sounds like you are a victim of international intrigue, or world economy at least. You have the right idea -- it takes impact to overcome the, ah, bond, that has developed between fastener and nutplate since its original torquing. But the world economy has blessed you with a substandard tool as it sounds in your post.

Can't tell you what Allen had in mind Mr. Torx tried to improve, but his wrenches should snap before they twist. And the fastener usually rounds out if brute force rather than impact is applied on a stuck one.

If the bolt is still usable, could you find a 5mm wrench by a good supplier? I have Craftsman, but probably old enough to be pre-Chinese if that makes a difference. I usually slip a nutdriver over the long end and use the ball of the hand to apply the impact (Karate Kid?) and there's a crack and she's loose. (whoa did I write that?)

If the bolt head no longer looks like Allen conceived it, you may need to apply Black and Decker to it and find some replacements at the boneyard. Yes, I know, bring your impact technique. I usually replace the damaged plastic collar with shrink sleeve.

Gotta go, Doug, but wishing you good luck,
--
Art Benstein near Baltimore