it's not truespace prob i think
ts automatically works with double side polys usually, if it doesn't it is probably because of
1 double side/single side option checked (if there is this option)
or
2 geo problem
first prob can be solved by flipping faces
second prob can be fixed by NOT using booleans
DON'T use booleans in this cases, just add verts/edges or use polydraw or connect manually the verts of two separated objects (after you unify them with boolys but maintaining them separated)
Using booleans it is very possible that the verts are not connected (two non connected verts share the same position and seem one single vert), in this case sometime the internal render of TS goes crazy, and it only partially render the wrong polys
BTW fs2 only support one side faces, so you will need two polys mirrored to make those fins visible from any angle