My question is: is their any way I may organize the modules or

indicate shared types in order to use a (very extensive) VB

interface (Or VB1 module)? Specifically how do I enforce the

shared type:

U1.instance VB1.t = U1.t = Make_U(VB1).t

First, try the above.  It may help.  If it does not, then you will need to add explicit sharing constraints.  But which sharing constraints are *really* needed will be the ones revealed by first removing the type annotations you currently have.

Worked correctly. However I need only remove the U in Make_U : U and
change it to a simple Make_U. "U1.t" now becomes visible and binds
correctly.