How to use differently sized static arrays per project

General Usage
4

What you mean here exactly? Three approaches could be used, I think:

  1. Annotate the parametric types on the functions (this one is the most elegant, in my opinion, since the function will specialize to that type of a anyway:
function f(a::A{N,T}) where {N,T}
   # use N here
end
  1. Get the size internaly:
function f(a)
   N = length(a.x) # a.x is the MVector{N,T}
   ...
end
  1. Annotate he size in your struct:
struct A{N,T}
   N::Int
   x::Vector{N,T}
end

and initialize it accordingly (and use a.N there)