Yeah they are solid. I add synthetic oil on threads then I work them in prior to installing. I also cut a few Millimeters off each side on the all ends all but the Steering setup.

Doing this prior prevents all the twisting once installed. I've also cut down a old turn buckle down before the Hex so I have only side with threads. Then I use a cordless drill with a socket that fit the hex part. Then I hold the plastic end with a adjustable wrench then I slow work them back a forth. Hope this helps. You can buy a turnbuckle bore bit believe Tamiya sells forget.