ZeroTier MTU issue?

Why is that the default MTU of ZT interface is 2800? Any way to change this? This is causing issues to some services we are accessing over VPN.

Also does anyone know how the MTU works over ZT? Seems like if I ping host over the same ZT network, I can ping them up to 2800 even with DF bit on. But anything behind those hosts, I can only ping them below 1472.