Multi 2D Ryall/Rigal

We use modified Muiderberg 2Heart/2Spade as our main preemptive weapon as this is more common than the standard six carder, and generally safer. We don't venture any weak major two on those tatty 5332 hands. It strikes me that you risk a penalty, but if opponents prefer (at their choice!) to overcall: their suits are breaking! This sounds like bad bridge to me.

EBU rules quite reasonably demand a reasonably frequent strong option in the Multi and that your major be ambiguous. We incorporate 22-24 balanced hands and big minor single suiters.

Our method allows you to show the following types

General method

The problem is there are just not enough simple levels at the 3 level to unravel all this, and explore the major's strength, and seek splinters, and still play in 3NT ... We get round this by ignoring(!) the major when suitable for 3NT, and a two way 3Diamond response to 2NT.

Our responses to the Multi 2Diamond (our weak option based on 5-9 non-vulnerable/vulnerable to 7-11 unfavorable)

Handling a big notrump hand
All is well over 2Heart/Spade responses - you just use your normal 2NT methods. It is important if you use the paradox preempts to agree a method over the 3NT strong balanced bid (many don't)! We use 4Club as simple 5 card Stayman, forcing to 4NT with no fit. 4Diamond/Heart as transfers and 4Spade as slam interest in both minors. Our 3NT-4Diamond preempt extensions allow opener to use judgment in these situation.
2NT general inquiry

2NT - inquiry, generally with 15+ or a good 9+ and both majors - responses:

When opponents bid

You must discuss what to do over opponents doubles and overcalls! After a double we make paradox raises as above (system on) on the basis that opener is almost certainly a weak two. Over major overcall it generally works to bid up in the other major, but you could come very unstuck! Perhaps for pairs competition only. We play double as penalty, but takeout double of 2Diamond - (2Heart/Spade) is a strong method. Over a double we make usual paradox response. 2Diamond - (DBL) - Pass = 5+ diamonds (playable). 2Diamond - (DBL) - ReDBL = 4+ diamonds but penalty orientated