I just checked mine (brand new with three flights on it), and I can wiggle the servo a little bit using just my a two-finger grip. It's actually the entire side of the fuse that moves. As you say, there isn't a lot of wood in front of the servo, so the side tends to have a bit of "give". However, if your servo wiggles while you move it, it probably means you have a binding somewhere and that force is transferred to the fuse. Mine doesn't do that, even though the fuse side has a bit of flex.
You're right about it feeling big! Wait til you fly it! In terms of size, it feels very similar to my 58" Edge and has none of the "small plane twitchiness". Actually, the 51" Slick probably tracks a little better than the 58" Edge. Hard to say, though, as they are both amazingly good airframes in my lowly and humble opinion!