I'm putting Ernie Ball 10 though 52s on my USA strat. I've used 9s in the past but wanted a little beefier tone. The 52 gauge string is pretty thick and doesn't seem to sit in the nut of my strat as far as they did in my les paul. How can I tell if the strings are fitting properly in the nut? Is there a rule of thumb such as they should be completely in the nut, half way in, etc?

Thank you.
tens aren't that heavy, unless they like pop out of the nut when playing or something, you'll be fine. you might see about getting the intonation checked though, different guages intone differently.
My Gear:
Fender Stratocaster Deluxe HSS
Hagstrom HIIN
Crate Palomino V32H w/ matching cab.
Roland Cube 60
Roland Micro Cube
Digitech Bad Monkey
Art and Lutherie acoustic