A lot of the reason most pro shops use left helical where you are is because most of their customers use left helical. And then, more customers will use left helical if the shops use left helical and only stock left wing feathers.

Around here, it's exactly the opposite. The shops fletch right helical and stock right wing feathers.

It's a regional thing.

Really, left or right helical is absolutely meaningless for everyone except those precious few who still shoot selfbows and use their knuckle for a rest.

The bit about right wing feathers keeping points tight and left wing loosening them is a load of manure. It's one of the many things people hear and then repeat it, over and over again. When enough people keep saying it, then it miraculously becomes 'truth' even though it has no basis in fact. I use right wing feathers and am constantly tightening up my points if I don't dope the threads with string wax.

If you like feathers, stick with them. They have many more advantages than disadvantages. Vanes only have one great advantage: they're waterproof. Check the shops to find out what's most available locally (probably left wing) and buy your jig to use them. It's best to be set up to use what they sell. Even if you go mail order, some day you'll find yourself in an emergency and wind up having to use what you can run to the store to get. You don't want a right wing clamp and only be able to get left wing feathers.