In a large bowl, combine the whole wheat flour, 2 cups bread flour, flax, gluten, yeast and salt. In a small saucepan, heat the water, oil, honey and lemon juice to 120°-130°. Add to dry ingredients; beat just until moistened. Add egg; beat until smooth. Stir in enough remaining bread flour to form a stiff dough (dough will be sticky).
Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease the top. Cover and let rise for 1 hour or until doubled.
Meanwhile, combine filling ingredients; set aside.
Punch dough down. Turn onto a lightly floured surface; divide dough in half. Roll each half into a 14x8-in rectangle. Sprinkle half of the filling over each rectangle to within 1/2 in. of edges. Roll up, jelly-roll style, starting with a short side. Pinch to seal. Place each loaf seam-side down in a greased 9x5-in. loaf pan. Cover and let rise until doubled, about 1 hour.
Bake at 350° for 34-38 minutes or until golden brown. Remove from pans to wire racks to cool.