Since the TVS devices are on the output side you can put them on the outside although this is not very convenient for the other wires. I routinely do this to test the circuits with trains once I have made the initial cut in the offending circuit. I do replace them however since I find internal protection a lot less clumsy than external. As John said the job can be done from the top you just have to use a low wattage iron and be really careful not to overheat the board.
Rolland
