Would the lens be too heavy to lug around for a 5 hr event?
I have puny arms too. I have done 10 hours weddings with a Canon 70-200 F2.8L before. With this lens, about 8 hours. Get a good camera strap that distributes the weight. With any event, you won't be solely using 50-140mm all the time. I usually alternate it with a prime or the 16-55mm.