The more blunt ends to the Femmax dilators could be helpful for some as it makes the initial penetration through the vaginal opening wider than a very tapered tip, so you get used to something much larger first entering the vagina. This is how the syracuse medical dilators are also made, and I have had good success using them with patients.
However, if you continue to just increase in dilator size, as long as the dilator you are using, whether more blunt end or tapered end, is wider than your partner, you should be ok.
You might need to dilate larger than the 5th Amielle dilator if you partner is bigger.