Not RA, but carpal tunnel gives me fits. That's why I build fat Tennessee handles on my spin rods.
I also use Wilson tennis racket grip wrap/tape from Walmart or Academy, secured fore and rear with a couple wraps of electrical tape. It's cushioned, "grippy", and adds diameter. Also about $5, so not a big loss if you don't like it.
Have used it on customs, couple of factory Loomis handles, and even a baitcaster or two.