You should have him get fitted.

Only way to be sure is to get on a trackman and test.

I agree we the other members, get on a trackman and see what the impact of a shaft change will do. If you move to the 6.0 LZ shaft you are going up in shaft weight as well.

Why are you thinking the shafts are too weak? Has his dispersion increased? Is he missing greens or losing distance or control?

It's not uncommon for a young player to out grow his equipment as they get stronger and a better swing. Get with his coach and get on a LM.

A lot of factors go into selecting the correct. Trackman will give you the numbers needed to select the correct shaft. I completely support having him see a fitter and checking his current numbers vs a potential new shaft. Ensure that he is an experienced certified Titleist fitter not a retail clerk at a big box store. With respect. =)

Just as every other reply you recieved, get your son fit by one of my fellow Titleist Fitters near you. Only way to see what truly fits him is to do a fitting. Your son is probably still growing so this should be accounted for during the fitting to help reach and obtain optimal data for him.