Looks like the image you have has the "heat-up and press the tubing flat" type ends like I surmised...

But I believe the other option '71Chop' was talking about would work something like THIS... I still think this would add unwanted stress points, but it's another option I could see working... perhaps bevel the edges of the insertion slugs to lessen the stress - just like insertion slugs for adding/patching frame tubing...

You could even drill and tap the end of the slug to thread on some sort of beauti-cap end...

I like my Women like I like my coffee... Cheap, Hot, and served to me by another Woman.

Ding Dang Motorpickle Project @#*!!...