Cool, that's a fair weather multi. I ask because we have lots of folks who don't make a connection with why their arm hurts, playing with 2 month old poly strung at 60 lbs. Here's some generalities, that are hinted at in the comments above. Heavy and head light are considered beneficial to tennis elbow, the extra weight makes the frame more stable and will absorb more shock, transfering less shock to the arm. Head heavy frames are generally considered poor choices for tennis elbow. Heavy frames can be detrimental to shoulder issues.
Also mentioned above, if you do add weight to the hoop, counter balance your weight in the handle to keep the frame head light. You could do this by switching to a thicker, squishier, heavier overgrip. Head hydrosorb, or Wilson shocksheild grips would add 5-10 grams and would absorb some vibration to boot.
As we all know, technique is a major factor. I used to play competitive table tennis, and I'd see guys playing with elbo straps! not much shock coming from a ping pong ball, and weight is not really an issue either. Sometimes it's ALL technique. On the other hand, this place is chock full of players who have had arm issues, and they disappear completely simply by switching racquets, string, or simply going back to whatever they used before the pain started.
Having said all of that, I have a hunch that taking some time off until the pain stops... then resuming play slowly with a full bed of gut, would be your best answer in terms of equipment changes. I think we just keep looking for other solutions that allow us to play through the pain because nobody wants to stop playing. Double that for not those of us who are so tennis obsessed (me) that we hang out here for kicks and giggles.
Hope this helps, good luck helping your guy.
- Jack