C.O.
most companies would rather have a happy employee than an unhappy one...if the company can do flex time - go for it...the worst they can do is say no...
I would ensure that my job gets done and that no one needs to take up the slack because of my hours...but I don't think you need to worry about that - you have said that you make up your time! :)
Communication is key - tell them what you need and what you will do for them!!