"The Parker arrows do have brass inserts."

No...they do not. The old Parker arrows were Bemans and the new ones are Carbon Express, but neither have brass, they have aluminum. I, for example, when I sell a Parker I include Gold tip arrows which have a brass insert. With that heavier insert a 100gr tip works very well. With an aluminum insert you will be better off using a 125gr tip just to put more weight forward on the arrow so it flys better. The weight of the tip will not be a huge factor in its ability to cut, but if a heavier tip makes it more accurate then it is well worth the extra mass....
Wyvern