Unfortunately, the PrincipledBsdf was introduced in P12 and, as you noticed, is absent in P11.  Your approach is acceptable, that is the common way of utilizing a transparency map for both Firefly and Superfly.  In Cycles, you can simplify the node arrangement as below:

Your Alpha map is plugged into the Fac channel of the MixClosure with the TransparentBsdf node just under that and followed by your texture node.