You can use a pressure type stop switch anywhere in the system..It makes sense to keep it closer to the master cylinder..mainly for shorter wire thats needed.. Unless you have a hydrovac ..The switch must be on the brake light side ..Most have a 1/8 pipe thread so a block with three outlets is needed..One wire is hot all the time,The other to the stop lights...

If all the cylinders ain't in a line it ain't cuttin it..