Marshall SV20H handwired

[MRX2099]

If I wanted to do a clone of the Marshall SV20H but hand wired with the presence knob and 4 holes, cause I don't want the new boards that are in them, and want to make my own (already built a 50Watt Plexi clone, and started a 18watt TMB combo amp years ago but never finished it) and want that small room sound, that I could crank and get the EVH tone without blowing out the neighbors. Could I just use the 50watt plexi layout and just use either 18watt or 20 watt transformers, or add a presence know in the 18watt layout, I want just the head no a combo amp but want that 4 hole plexi n a 18 or 20 watt version like the SV20H. Any help is appreciated