I am left handed, play accordion and guitar right handed. I can't say that I have a problem. It took a while to develove the use of all my fingers. I don't think it makes a difference which hand is used to play the treble side. I think it just takes time to develope the physcal ability in each finger of whichever hand you use.
If you find that you have trouble with one of your fingers, then you might spend some time working on that finger. I know that's what I had to do.
Jude

Jude have you ever heard of someone making a left handed accordion? Have you ever considered it? Just curious.

I've got a hand exerciser, to develop the right hand, and I tried it on my left hand the other day, and I'm considerably stronger in that left hand. I'll just keep working it.

I drive the freeway a lot, and that left hand gets quite a workout gesturing to other drivers.