[Therion] "Passage height" question

Hello everyone - I have a question about the point type "Passage height". I am working on a map which has some ceiling heights under 1 foot. When I put in "-value [0.5 ft]", for example, it comes out on the map as zero, or "-value [1.5 ft]" comes out as 2. Is there a way to make those come out with the value given? There is a passage section which has a voice and light connection, about 35 feet long and 6 or 8 feet wide but only 6 inches high. It is not human passable, but we can talk through it. I want to indicate its height correctly. Thanks - Bill Gee