Cast and palm swell...
And yes, it makes a difference. I recently switched out the wood on my SP I to lefty wood I no longer have to fight to get a proper cheek weld and sight down the rib. Mounting the gun properly is a snap!
Now, if it actually improves my shooting is yet to be determined. But I can no longer blame the gun... RATS!
Good to hear the LH stock is working for you.
(I am the guy you bought it from awhile back).
I finally installed it over New Year's weekend. I was going to wait till the weather turned bad and send it to Beretta to have it done, but everyone kept saying it was an easy home project.
I did have on major snafu, when trying to enlarge the holes for the recoil pad screws (the walnut is such a hard wood, the screws were stripping), I snapped off a drill bit in the stock. I had to drill it out, plug the hole and re drill a new hole. I took the better part of the weekend, but I finally got it done. You can only see my screw-up if you take the recoil pad off. Otherwise, it's hidden.
I also had to file/sand down the fore-end a bit, as it was very tight and difficult to attach. But, slow and steady, it fits perfectly now!