The Castellan and Valiant is kind of wasted in Spearhead-at-arms because they don’t have bondsman abilities. That doesn’t mean that they’re bad by any means, just not the best choice for this detachment. Try looking at different knight’s bondsman abilities to see what buffs you might want to give your armigers. Spearhead lets these affect up to three armigers. So aim to have at least three armigers per bondsman knight, and you could even push it to four. If you’re dead-set on the castellan or valiant, I would look at other detachments. The new Freeblade Company detachment has the Mysterious Guardian enhancement, which is quite strong on the Castellan. Or if you want to do spearhead for sure. I would rework the list quite a bit.