[Grammar] I shouldn't wonder if you didn't make/made

[suprunp]

[A heroine's mother talking to a would-be son-in-law] And take it all in all I don’t dislike you. I shouldn’t wonder if you didn’t make Annette a better husband than that teacher. And with the baby coming and all.’
(W.S. Maugham; The Unconquered)

I would surmise from the surrounding context, which can't be revealed through these three sentences, that she thinks he would make Annette a better husband than 'that teacher'. But why doesn't she say "I shouldn't wonder if you made..."?

I infer that the variant in the original sentence is used as well, but how would you express this thought?

Thanks.

 

[BobK]

I would probably use 'made', but there's a tendency to slip into the present - especially in speech.

b

 

[5jj]

This negative construction when logic tells you it should be affirmative is strange, but not uncommon with 'I shouldn't wonder/be surprised ...'