Hi – Is anyone aware of a design for a backhead fitting blow down valve for a model steam locomotive in 3.5”/5” gauges similar in action to that shown on page 165 of Martin Evan’s book “The Model Steam Locomotive” but with access to the valve from above instead of from the front. Reason for the proposed change is to ease the handling arrangements from what would be a cramped footplate. Will be interested to see what my options are.