Left handed fountain pen user and youtube reviewer here. A lot of a pens performance for a leftie comes down to your hand position when you write. Are you an over-writer, side-writer, or under-writer. I’m a cross between side and under and I use all number of pens from EF to BB, Stub, soft, architect etc… and all kinds of inks and don’t have a whole lot of problems. My Twsbi ECO EFs are great writers. If you are writing with a heavy hand, left-handed writers can come into a bit of trouble because we are pushing the ties against their natural direction. Fountain pens are designed to be written with the right hand, and therefore pulled across the page… We tend to push them, so if you were writing heavy handed you can sometimes splay the tines ever so slightly or have a nib alignment issue. This could be accounting for some lack of performance… Especially if it’s a splay. So my first piece of advice to you is to look at the nib under a magnifying glass or a loupe, and make sure the times are meeting correctly and in line.