I cleaned and then primed inside these relatively small diameter tubes using a shotgun cleaning rod & wipes. First saturated in Acetone couple passes, then couple passes with saturated cloth in Primer. Worked really well.
Then riveted with long -11 rivets (470 4 size). As noted in instructions, these really want to bend over. So I proceeded via small incremental "squeezes", varying slightly the alignment to keep moving the shop end back toward center. With some practice, I applied quick short "hits" with small orientation changes in rapid progression. All but couple ended up oval shaped, but confident very stout.
Installed Rod End Bearings with jam nuts - being sure each end was "clocked" 90 degrees.
Then AAARRRGGGHHH... began preparing for next Section, and couldn't find Bellcranks. I'd forgot these are on BackOrder from Vans. Sent email for update, and will work on other sections.