Nesting box, Releasing, and fear of people

[lnswiger]

Hey everyone
I am getting ready to release my two sweet little monsters, and wanted to get a nest box for them now to get used to while they are still in the cage. All the ones I've seen online the entry hole looks very small, especially for my biggest little monster. Just wondering if anyone had any suggestions for nest boxes, and for releasing in general!
Thanks in advance!

Just a bit of info:
They are both Grey Squirrels, one about 6 mo (male), the other about 4 mo (female). They primarily are indoors now, with a big cage and a room to themselves to run and and destroy. They have an outdoor cage where they spend at least an hour or so outdoors each day, and the releasing plan is to slowly allow them to be outside in their cage more and more, until I open the door and let them run out, while still having the cage there for them to come back. I'll install the nest box in the tree (they will be released into my backyard, with lots of big oak trees to play in), and of course I'l continue to feed my little babies while they are outdoors. My timeline for this is end of September, I live in Texas so I am just waiting for it to cool down a bit before I release them.
The only qualm I have about releasing is that the older male, (named Ghost) doesn't really have a fear of people. Its been that way since day one, which is actually how we got him. When he was about 3 mo he was just laying in the backyard for hours making no noise until I finally went up and scooped him up and took him inside. He will let anyone touch him, and he'll climb over you and sit on your shoulder. He's a real sweetheart, I just fear that this will get him into trouble once released.
Sorry for the long post, I just want to do what is best for my babies!
Like I said, any and all advice will be appreciated!

[Spanky]

You want the box to be deep with an internal predator guard to prevent racoons from being able to reach into the lower part of the box. I like the boxes made by Coveside but I modify them now with an external predator guard, a portal guard and I add a "porch".

http://www.amazon.com/Coveside-Pet-H...irrel+nest+box

One of mine after modifications:


Nuts about squirrels offers great boxes too:
http://nutsaboutsquirrels.net/#!/Nesting-Boxes/c/9506014/offset=0&sort=normal

I would not worry about them being able to enter the 3" hole, that should be plenty large enough.

You may want to consider starting the soft release process sooner, since after several weeks outside when you finally open the release cage you want them to have enough time to build up a food stash for winter!