Section G_subst.
rewrite <-T_ren with (delta := add 2).
unfold T. eapply equiv_join.
cbn. do 3 (dostep; cbn). unfold beta. rewrite rinstInst_exp, !compComp_exp. reflexivity.
eapply refl_star. eapply ext_exp.
intros [|[|[]]]; cbn; eauto. now asimpl.
Qed.

Lemma G_right_subst m: (T m) Nil (enc n A) (Succ B) ≡ τ • lin (tab t m) r.