What size heat shrink (in mm) for a de-pinned X4RSB?

I want to de-pin my X4RSB, but I'm not sure what size heat shrink I will need. I asked around at a race the other day, and some people told me to use 30mm, and some told me to use 50mm. Obviously I can't use heat shrink that's too small, but I also don't want to get heat shrink that's way too big and get a loose fit around the receiver, so... which is it? 30mm or 50mm?