Can't say for sure but I'd guess from how my unit cuts 1 1/2" might be a safe
cut for you so long as the shear bolt is the correct size and will let loose if you hit something to big. Last year I hit a steel fence post that was hidden along a fence and almost
cut it in half, made one **** of a noise and it put a dent in the top cover, blade got a nice nick in it now but it didn't stop it. It's going to depend on how you hit anything and you speed.
If in doubt get your self a chain saw and play it safe.