how much cloak do you need for someone to never scan it?

I believe the number is close to 15k (after legion bonus). So the answer is it can be done but in doing so, you will not get enough resources to make the planet worth it.

Well i know of two planets found with over 20k cloak so hey chances are low tho at that piont

That is surprising... with Dan's formula, they should never be found.

Even with them found you still have to go through 10000 defense and 10000 attack. If you talking about the Dysons or terra forming planets.. then again not worth it for production wise.

I know one with over 20k worth of cloak and was still found and taken... now I just gave up in cloak.
I used to push it hard but now, naw.

Are you sure it was found after it had that cloak, and not before?

I can't say that I do know that, I just know that it was 'found' and taken.
The highest cloaked planet I have found is a little less than 5000. I am torn between believing or not...