I hear your disappointment. I really do. I don't want anyone who wants to shoot to be excluded. I have wrestled with the issue you are asking about ever since our first event in 2016.
I have been ripped apart on both sides of the question. So as it stands for now, no tube inserts that are not permanent to that gun/ barrel. Now I will tell you no one will be checking equipment unless there is a complaint filed against a shooter and I personally don't see that happening. Remember this is for fun and enjoyment and friendly good hearted but serious competition. Please find me at the shoot and I will be happy to talk to you about your concerns.
All my best,