I think you might be over thinking the attachement of the 2 inch pipe. Other than esthetics I don't see why you need to center it, your tower legs are vertical and the cross section of the tower is not very large (I'm assuming you will be guying it off anyway) . I would get some U bolts, say 4 of them with longer legs, lay the pipe on the inside of your tower against one of the legs, so that it will extend down past 2 or more lattice sections , lets say 4 or 5 feet (I don't know the spacing on the lattice), then place the u-bolts over the 2 inch pipe and the leg, and tighten. This is safer than a single attachement point on the plate as now your pipe will distribute horizontal force to the leg, which is actually the entire tower due to the lattice.
I would probably place the pipe against the union of the lattice and the leg and through bolt once or twice through the leg and the pipe.
You could at that point add some welds, and if your worried about the lattice strength, reinforce it with some angle iron.