I have had flexible extenders on several motorhomes with zero issues. But... i just had the Michelin recall done (Feb.) and found both inner tires flat one morning post the new tires being installed. I figured they were just poorly installed and really put the pliers onto them. One has held air but the other one has subsequently gone flat again. I have ordered new more expensive extenders to see how they work. It is a real pain without them so need to install something.
Are you able to reach the inner wheel stem to tighten the extension without removing the outer?
What did you order and keep us posted on how you like them.
Your experience makes me want to order new extensions when I replace the tires.