I just did a simple experiment. I exported the default Blender cube. It is simple, only the 8 necessary vertices. Inside Blender it is interpreted to be 2 units per side, a unit in Blender is 1 meter. Looking at the exported .obj file using a text editor, I can see the vertex data using 1 and -1 values. So this is consistent 1 to -1 is two units. The geometry described is two units per side, centered around 0,0,0. I import this obj into Poser. Now Poser interprets it as a cube, two units per side. A Poser unit is 8.6 feet or 2.6218 meters. A cube that is 2 units per side therefore shows up in Poser as 5.24256 meters per side. So what you can do is determine what a native Hexagon unit is in relation to feet or meters. Then you will know what scale factor to apply either at the Poser export or the Hexagon import. If you use a simple 8 vertices cube, import into Hexagon, use a measuring tool in Hexagon or view the size somehow, then you will know how a unit is represented in Hexagon and can compare that with Poser's unit to determine the scale factor.

Save the below text as a BlenderDefaultBox.obj file, and it can be your test file.

# www.blender.org
o Cube
v 1.000000 1.000000 -1.000000
v 1.000000 -1.000000 -1.000000
v 1.000000 1.000000 1.000000
v 1.000000 -1.000000 1.000000
v -1.000000 1.000000 -1.000000
v -1.000000 -1.000000 -1.000000
v -1.000000 1.000000 1.000000
v -1.000000 -1.000000 1.000000
s off
f 1 5 7 3
f 4 3 7 8
f 8 7 5 6
f 6 2 4 8
f 2 1 3 4
f 6 5 1 2