Wouterf

Well in matchpoint bidding 1D can be very beneficial if partner has the 18-19bal. Auction will often go 1C-1D-1NT (opps dont bid anything so p is often strong), which pays a lot more than 1C. Also (non-vulnerable) bidding might bluff your opps out of their contract.

Ik dont have the system in writing but I can help a bit with the follow up. 1C = 2+ crd, natural or 12-14nt without 5crdM or D, or 18-19bal (this one can have 5crd D) (when 1NT is 10-12 or 12-14, then the weak bal becomes 13-16 or 15-17, strong is always 18-19 and sometimes 18-20) 1C-1D; 1H = Clubs + hearts (unbalanced, could be 4414or1444shape), or weak NT. 1C-1D; 1NT = Strong NT (18-19bal can still have 5D). 1C-1D; 1H-1S = Relay. 1C-1D; 1H-1NT = 4-4 majors (0-10hcp). 1C-1D; 1H--- 1S = Relay. Which strong/weak hands are included? - Pretty much every strong hand, hands that pass 1NT and very weak ones with 5crdM(0-6)hcp ..1NT = Weak NT. Now what? Can the weak hand sign off? Perhaps weak/strong transfers? - The game continues as if p opened 1NT, so stayman and tranfers (very weak 5M transfers). ..2C = Limited with clubs and hearts? What is the maximum? - 2 weak for a reverse, so 11-15ish ..2X = Stronger with clubs and hearts? - Yes, usually paterning out, bidding a 3crd spade or diamond suit or 4441type shape 16+hcp. 1NT = 4-4 majors, 0-10 hcp. Perhaps weak hands with say 4H and 5S bids this too? - Usually 4-4 only. Other option is 2 simply relay and bid stayman after 1NT (garbage stayman) or jacoby transfer. Does opener's 1M bid have a limit (if unbalanced), or is it 11-22? - 11-22 :) 2C = My guess is that this shows both minors, but no idea about what kind of strength. Another option could be something artificial with diamonds, and GF. - This tends to just show 5 clubs and 0-6 2D = Natural? But what tempo? - Diamonds natural and weakish, TP versus 12-14bal so 0-9hcp 2M = ?? - Doesnt exist, but I have seen some agreements as shortness and invite+ or weak with both minors. Some further details: a 2NT rebid by opener after 1M shows 3M6m or 4M5m and strong. so 1C-1H-2NT= 16+ with 5+Cand3-4H 1C-1H-2D= either a normal reverse, or 18-19bal 1D-1M-2NT= also 16+with 5+D and 3-4M. This is the reason why all 18-19bal are opened with 1C (and can still have 5D)

https://www.larryco.com/bridge-articles/the-most-successful-openings This is a small article from Larry Cohen which I really like. It describes the habit of opening light. Basically as long as you and your p agree on light openings, meaning an opening versus an opening doesnt nessesarily mean game, it simply pays to open the bidding as much as possible. It puts your opponents on defense, disrupts their constructive bidding and makes defending easier.

3♣ seems standard, don't punish p for making a balancing bid. He is bidding on your hcp as well. Not all games are ment to be bid.

Muiderberg and other 2suited preempts are basically like any other weak two bid. Points in your long suits are very strongly prefered but never having anything outside lowers the frequency way to much. It is simply a matter of counting positive aspects (singleton, hcp in long suit, no aces etc) to the negative ones (5422 shape, point outside long suits, aces etc) When it comes to Muiderberg it is esspecially important that your M suit is good, since partner will very often pass 2♠ with say a 2434 12count. You will therefore play the 5-2fit very often. As for your p, his argument has some merit but his bidding is still way to pessimistic, why should p always have a 5422 shape? something like QJxxx-x-K10xx-xxx already makes a very decent game.