What THWACK! said. I just posted a slingbow arrow prototype in the Slingbow sub-forum. Ghost0311/8541 posted his version. I am working on a short arrow design that can be shot w/ a cheap mechanical archery release. Since the arrow is short and light, it can be launched w/ very light office rubber bands.
Apologizing in advance for getting all "woo-woo" but have you tried alternative medicine? Chiropractic, Ayurvedic, Acupuncture, Homeopathic, etc. Allopathic (Western) medicine really does not have an answer when arthritis gets as bad as you described. I know two Acupuncturists, one is an archer and the other is an edged weapon guy. Both keep me going as I begin my dotage. To quote my Chiropractor "at your age if you are not moving, you're dead."