/2 width=5 by tri_TC_strap/ qed-.
lemma fqus_drop: ∀G1,G2,K1,K2,T1,T2. ⦃G1, K1, T1⦄ ⊐* ⦃G2, K2, T2⦄ →
- ∀L1,U1,e. ⬇[e] L1 ≡ K1 → ⬆[0, e] T1 ≡ U1 →
+ ∀L1,U1,m. ⬇[m] L1 ≡ K1 → ⬆[0, m] T1 ≡ U1 →
⦃G1, L1, U1⦄ ⊐* ⦃G2, K2, T2⦄.
#G1 #G2 #K1 #K2 #T1 #T2 #H @(fqus_ind … H) -G2 -K2 -T2
/3 width=5 by fqus_strap1, fquq_fqus, fquq_drop/