RE: Den trees
...just remember that everything you do has benefits and consequences. It's a very good thing to have biodiversity, but this will do more than just increase the abundance of squirrels and some non-game species. It will also reduce forest health and increase the number of predators that prey upon the eggs of gallinaceous birds such as quail and turkeys. It's a trade-off and you must decide what your ultimate goals are before performing an action like this then make an allowance for exactly how much effect this could have based on the current trends toward your main objectives.
...not a criticism of what you're doing, by the way, Robertesq1...just pointing that out so everyone makes the connection on the trade-offs associated with it...I think you're doing much good for some of the critters.