I use the old Duboin-Bocchi scheme: 1♦-2♣: a) GF without 5M :) INV with 6♣ c) INV with 4+♦ d) BAL INV Development: 1♦-2♣ 2♦: 11-15, any 2-suiter or 3-suiter 2♥: one-suiter or 12-14 balanced 2♠: clubs, 16+ 2NT: hearts, 16+ 3♣: 5♦4♠, 16+ 3♦: 6♦4♠, 15+ 3♥: 6♦5♠, 14+ 3♠: 4450, 15-17 After the potentially weak rebids of 2♦ and 2♥: 1st step: GF relay 2NT: BAL INV 3♣: 6♣ INV 3♦: 4+♦ INV