no, those sound about right.
it is a woofer/tweeter set up, Im home but I cannot find my security torx bits so I cant get the mesh off and I dont see anything in the book with sizes. just get a speaker that wont fall through the hole and you should be ok =) or msg mk3fan he has a MK1,2,4 dedicated and he build his own UMK3 so he should definitely know