Odd Dog peeing behavior

Question
So we have had our now year old boxer for four months now.  He sleeps in his crate through the night very well without having any accidents (even so well that we now leave the door open every once in a while).  My husband goes to work at 5am and used to let him out then, but he has gotten to the point where he is tired and just wants to wait till i get up later, so he can obviously comfortably hold it.

He had a few accidents in the house when we first got him, but not for the past couple months.  He generally goes to the door if he has to go, and gets let out in the fenced yard every three to four hours.  Our only problem is with him peeing while he is in his crate and we are not home.  He does this whether he is left there for a 8 hours or 2.  The weird thing is, most of the time, it's not that much (not like a full bladder that he couldn't hold), and he tries to aim it outside of his crate.  We even switched from a wire crate to a plastic one and even though it is the right size, he's a boxer and has found a way to configure himself so that he can pee out the front gate.  The thing is sometimes, we only see drops on the edge of the crate and the carpet isn't wet, but we can smell it.  We've put paper towls infront of the crate and when we get home, there is only a very tiny yellow area on them.  I have no idea what he is trying to accomplish or why how to get him to stop.  Ideally, we want him to be able to roam the house while we are gone like our other dog, as a boxer of all dogs, should not be cooped up all day.

Answer
Any time you have a new urination behavior, its a good idea to get a vet check up to make sure it's not a physical issue (got in one rescue with bladder stones whose "symptom" was that he lifted his leg everywhere.
If it's just a little bit, it sounds like he is starting to mark (he's the right age for that)Is he neutered? Sometimes that decreases marking, but not always. Do you think he would leave a belly band alone? That might be something to try, but I would have him wear it first when you can supervise, to make sure he doesn't tear it off and eat it.
Of course,once a dog is marking a location, he will smell his scent and mark it again. A good enzymatic product will help, but it's a problem when the dog does something unsupervised. The only effective way to train is if you can stop what's going on when it happens. After the fact does no good.
Sandy Case BFA, MEd CPDT www.positivelycanine.net