sometimes, hi-res prims are just connected directly...
this can still cause gaps at higher prim substitutions.
in normal res, this could be solved with an ering (manually drawn p16 vertices inside, outside scalable, normally invisible).
on 16->48 prim subst, this gets replaced with an aring (p16 inside, p48 outside).
the same aring gets invisible at this prim subst (because inside and outside prims are now both p48).
in your case, we would need something like a hi-res ering (manually drawn p48 inside, outside scalable).
While we are at it, we could even need a hi-res tang (a p96 outer polygon) for even thinner gaps (if a normal tang is too wide or at different angles).
this can still cause gaps at higher prim substitutions.
in normal res, this could be solved with an ering (manually drawn p16 vertices inside, outside scalable, normally invisible).
on 16->48 prim subst, this gets replaced with an aring (p16 inside, p48 outside).
the same aring gets invisible at this prim subst (because inside and outside prims are now both p48).
in your case, we would need something like a hi-res ering (manually drawn p48 inside, outside scalable).
While we are at it, we could even need a hi-res tang (a p96 outer polygon) for even thinner gaps (if a normal tang is too wide or at different angles).