Zelandakh, on 2015-August-27, 08:57, said:
You have no call to show a major in this scheme and this is generally regarded as a very important hand type. You could take away 2♦ for that purpose and make the double diamonds + a rounded suit. That would certainly give you a call for all one and two suited hands, albeit with the usual caveat of not being able to differentiate lengths at all between those two suits.
 
By which I take it you mean no call to show a single-suited major, such as the 2D bid in Multi-Landy?
Yes, you're correct. 
So, Dbl could be Minors, as I've stated above, 
OR a single suited 
♥ or 
♠. Advancer, chooses his favoured Minor and now I correct to the long major. Make sense?
Also, by using Dbl for the Minors, Advancer can now use 2NT as a forward moving inquiry bid.
So, in summary.....
Dbl         = Minors or long 
♥ or long 
♠. If it's a Major, doubler corrects after Advancer has chosen his Minor.
2
♣    = Majors (with 2
♦ relay)
2
♦ = 
♦ and 
♥
2
♥   = 
♥   and 
♣
2
♠   = 
♠ and 
♦ or 
♣
2NT is Advancer's inquiry bid.
D.