Principle

/2♦ can have 5 possible meanings:

A. 7-11, 6-♥♠

B. 23+, game forcing

C. 20-22, Non-Balanced

D. 25+, Balanced

E. 16+ unicolor, 10-11 tricks

A. 7-11, 6-♥♠: /2♦ - 2♥♠ - PASS/2♠

B. 23+, Game Forcing: /2♦ - 2♥♠ / 3♣♦♥♠

C. 20-22, Non-Balanced: /2♦ - 2♥♠ / 2NT

Principle

3♣ Niemijer inquires for a 4- or 5+card M, while a followup 4♣ is a classical Minor Suit Ask if one 5+card is known, or a custom Minor Suit Ask if there's no 5+card know yet.

/2♦ - 2♥♠ / 2NT

- 3♣: Niemijer

/ 3♦: 4-card M, same as classical classical Niemijer

/ 3♥: 5+card ♥

- 4♣: classical MSA

/ 4♦: 5+card m

- 4♥: which 5+card m?

/ 4♠: 5+♣

/ 4NT: 5+♦

/ 4♥: 4-♣

/ 4♠: 4-♦

/ 4NT: 4-♣ and 4-♦

/ 3♠: 0-1♥, 5+♠

- 4♣: classical MSA ...

/ 3NT: no 4-M (5+4+ or 5+5+ m)

- 4♣: custom MSA, nothing known about a 5+card yet, 5+card?

/ 4♦: 5+♣ and 5+♦

/ 4♥: 5+♣

/ 4♠: 5+♦

/ 4♣: 5+♥ and 4-♠

/ 4♦: 5+♠ and 4-♥

/ 4♥: 5+♥ and 5+♠

- 3♦: transfer for ♥

/ 3♠: transfer refusal, 0-1 ♥, 5+♠

/ 3NT: transfer refusal, 0-1 ♥, 0-4♠, 5+m

- 4♣: custom MSA, nothing known about a 5+card yet, 5+card?

/ 4♦: 5+♣ and 5+♦

/ 4♥: 5+♣

/ 4♠: 5+♦

D. 25+, Balanced: /2♦ - 2♥♠ / 3NT

Principle

Simply followed by Stayman via - 3♣ and Jacoby Transfers via -3♦♥♠♣

E. 16+, to-11 tricks: /2♦ - 2♥♠ / 4♣♦♥♠