craftgrrl | felt on an acrylic scarf question

Hi all,
I have knitted up a white acrylic scarf, and I wanted to add some letters to it. I was planning to cut them out from felt I have and sew them on. Will the scarf still be machine washable? Will the felt bits just kind of....fuse onto the acrylic? (that's what I'm hoping will happen)
Or will the felt completely morph/shrink/screw up the scarf (change it's shape, etc).
I have t-shirt fabric to use as a backup, but I'd really rather use the felt, and I'd like to keep the scarf machine washable.
Thanks!

And on another note, I just wrote up my list of X-mas presents I still have to make, oh god! Panic time!