Okay, now, I don't know if you've read "Hannibal", but whatsisname, Thomas Harris or whatever, he has a tendency in that book to jump between present and past tense from chapter to chapter. When I started reading it and noticed this I got a bit grumpy. "How sloppy!" I thought. BUT. The more I read of it, the more I liked it, and the more it seemed to well illustrate the story he wanted to tell. I ended up very glad that he'd done it that way. It gave the book an extra bit of depth and strength.

So if it works, go with it.