Gunsmithing Seekins sling rail mount to flush cup

[radmcg]

I have a A5 with a single stud and a flush cup on the bottom of the forend. I have seekins sling rails on all my other rifles and want to mount one on my 300. Does anyone make a flush cup insert that is or could be threaded. The front stud and the flush cup lineup perfect if I could just get something threaded to go in the flush cup so I could mount the rear screw. I dont have a flush cup sling swivel to see if they are threaded for the sling loop or how they are attached.
AHA
Rad