I’ve been toying with something similar for my Use Tula’s but the armrests only mount with one bolt so the extra leverage would put a huge strain on it.
If I do end up doing it my plan is to bridge all the way across with a strip (or strips) of steel/ally to spread the load a bit better. Sprayed black I think it would be quite discreet but may interfer with hydration/computer mounts if you have anything like that in the area.
Clearly not cheap, but the official aerobars that I see Specialized triathletes using look pretty wide.
I guess the only think you might be able to do is use some kind of bridge to attach to the clamp, and then attach the arm rests onto that bridge. I’d imagine being so far from the clamp they’d be a bit “bouncy” tho
I’m looking to put Di2 shifters on so the official £300(!) clip-ons are no go (closed loop stuff). Along with a disc rear it’ll make my Venge a hilly TT option, or simply a good long distance tool (TriX, Wales etc).